diff --git a/README.md b/README.md
index eae9860..610ad5d 100644
--- a/README.md
+++ b/README.md
@@ -14,15 +14,23 @@ Fetches and creates versioned GitHub resources.
 
 ## Behavior
 
-### `check`: Extract versions from the bucket.
+### `check`: Check for released versions.
 
-*TODO*
+Releases are listed and sorted by their tag, using
+[semver](http://semver.org) semantics if possible.
 
-### `in`: Fetch an object from the bucket.
+### `in`: Fetch assets from a release.
 
-*TODO*
+Fetches artifacts from the given release version. If the version is not
+specified, the latest version is chosen using [semver](http://semver.org)
+semantics.
 
-### `out`: Upload an object to the bucket.
+#### Parameters
+
+* `globs`: *Optional.* A list of globs for files that will be downloaded from
+  the release. If not specified, all assets will be fetched.
+
+### `out`: Publish a release.
 
 Given a name specified in `name`, a body specified in `body`, and the tag to use
 specified in `tag`, this creates a release on GitHub then uploads the files
diff --git a/check_command.go b/check_command.go
index 47f1687..f5e8f4a 100644
--- a/check_command.go
+++ b/check_command.go
@@ -72,12 +72,12 @@ func (r byVersion) Less(i, j int) bool {
 		return false
 	}
 
-	first, err := semver.New(*r[i].TagName)
+	first, err := semver.New(dropLeadingAlpha(*r[i].TagName))
 	if err != nil {
 		return true
 	}
 
-	second, err := semver.New(*r[j].TagName)
+	second, err := semver.New(dropLeadingAlpha(*r[j].TagName))
 	if err != nil {
 		return false
 	}
diff --git a/check_command_test.go b/check_command_test.go
index 817165c..76c6969 100644
--- a/check_command_test.go
+++ b/check_command_test.go
@@ -44,9 +44,9 @@ var _ = Describe("Check Command", func() {
 		Context("when there are releases", func() {
 			BeforeEach(func() {
 				returnedReleases = []github.RepositoryRelease{
-					{TagName: github.String("0.4.0")},
+					{TagName: github.String("v0.4.0")},
 					{TagName: github.String("0.1.3")},
-					{TagName: github.String("0.1.2")},
+					{TagName: github.String("v0.1.2")},
 				}
 			})
 
@@ -58,7 +58,7 @@ var _ = Describe("Check Command", func() {
 
 				Ω(response).Should(HaveLen(1))
 				Ω(response[0]).Should(Equal(resource.Version{
-					Tag: "0.4.0",
+					Tag: "v0.4.0",
 				}))
 			})
 		})
@@ -79,9 +79,9 @@ var _ = Describe("Check Command", func() {
 		Context("when there are releases", func() {
 			BeforeEach(func() {
 				returnedReleases = []github.RepositoryRelease{
-					{TagName: github.String("0.1.4")},
+					{TagName: github.String("v0.1.4")},
 					{TagName: github.String("0.4.0")},
-					{TagName: github.String("0.1.3")},
+					{TagName: github.String("v0.1.3")},
 					{TagName: github.String("0.1.2")},
 				}
 			})
@@ -104,13 +104,13 @@ var _ = Describe("Check Command", func() {
 
 				response, err := command.Run(resource.CheckRequest{
 					Version: resource.Version{
-						Tag: "0.1.3",
+						Tag: "v0.1.3",
 					},
 				})
 				Ω(err).ShouldNot(HaveOccurred())
 
 				Ω(response).Should(Equal([]resource.Version{
-					{Tag: "0.1.4"},
+					{Tag: "v0.1.4"},
 					{Tag: "0.4.0"},
 				}))
 			})
diff --git a/cmd/in/in.go b/cmd/in/in.go
new file mode 100644
index 0000000..6d7245b
--- /dev/null
+++ b/cmd/in/in.go
@@ -0,0 +1,41 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+
+	"github.com/concourse/github-release-resource"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		resource.Sayf("usage: %s <sources directory>\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	var request resource.InRequest
+	inputRequest(&request)
+
+	destDir := os.Args[1]
+
+	github := resource.NewGitHubClient(request.Source)
+	command := resource.NewInCommand(github)
+	response, err := command.Run(destDir, request)
+	if err != nil {
+		resource.Fatal("running command", err)
+	}
+
+	outputResponse(response)
+}
+
+func inputRequest(request *resource.InRequest) {
+	if err := json.NewDecoder(os.Stdin).Decode(request); err != nil {
+		resource.Fatal("reading request from stdin", err)
+	}
+}
+
+func outputResponse(response resource.InResponse) {
+	if err := json.NewEncoder(os.Stdout).Encode(response); err != nil {
+		resource.Fatal("writing response to stdout", err)
+	}
+}
diff --git a/fakes/fake_git_hub.go b/fakes/fake_git_hub.go
index 67dce0d..aa2fb14 100644
--- a/fakes/fake_git_hub.go
+++ b/fakes/fake_git_hub.go
@@ -26,6 +26,15 @@ type FakeGitHub struct {
 		result1 *github.RepositoryRelease
 		result2 error
 	}
+	ListReleaseAssetsStub        func(release *github.RepositoryRelease) ([]github.ReleaseAsset, error)
+	listReleaseAssetsMutex       sync.RWMutex
+	listReleaseAssetsArgsForCall []struct {
+		release *github.RepositoryRelease
+	}
+	listReleaseAssetsReturns struct {
+		result1 []github.ReleaseAsset
+		result2 error
+	}
 	UploadReleaseAssetStub        func(release *github.RepositoryRelease, name string, file *os.File) error
 	uploadReleaseAssetMutex       sync.RWMutex
 	uploadReleaseAssetArgsForCall []struct {
@@ -96,6 +105,39 @@ func (fake *FakeGitHub) CreateReleaseReturns(result1 *github.RepositoryRelease,
 	}{result1, result2}
 }
 
+func (fake *FakeGitHub) ListReleaseAssets(release *github.RepositoryRelease) ([]github.ReleaseAsset, error) {
+	fake.listReleaseAssetsMutex.Lock()
+	fake.listReleaseAssetsArgsForCall = append(fake.listReleaseAssetsArgsForCall, struct {
+		release *github.RepositoryRelease
+	}{release})
+	fake.listReleaseAssetsMutex.Unlock()
+	if fake.ListReleaseAssetsStub != nil {
+		return fake.ListReleaseAssetsStub(release)
+	} else {
+		return fake.listReleaseAssetsReturns.result1, fake.listReleaseAssetsReturns.result2
+	}
+}
+
+func (fake *FakeGitHub) ListReleaseAssetsCallCount() int {
+	fake.listReleaseAssetsMutex.RLock()
+	defer fake.listReleaseAssetsMutex.RUnlock()
+	return len(fake.listReleaseAssetsArgsForCall)
+}
+
+func (fake *FakeGitHub) ListReleaseAssetsArgsForCall(i int) *github.RepositoryRelease {
+	fake.listReleaseAssetsMutex.RLock()
+	defer fake.listReleaseAssetsMutex.RUnlock()
+	return fake.listReleaseAssetsArgsForCall[i].release
+}
+
+func (fake *FakeGitHub) ListReleaseAssetsReturns(result1 []github.ReleaseAsset, result2 error) {
+	fake.ListReleaseAssetsStub = nil
+	fake.listReleaseAssetsReturns = struct {
+		result1 []github.ReleaseAsset
+		result2 error
+	}{result1, result2}
+}
+
 func (fake *FakeGitHub) UploadReleaseAsset(release *github.RepositoryRelease, name string, file *os.File) error {
 	fake.uploadReleaseAssetMutex.Lock()
 	fake.uploadReleaseAssetArgsForCall = append(fake.uploadReleaseAssetArgsForCall, struct {
diff --git a/github.go b/github.go
index d227c2b..90dddd5 100644
--- a/github.go
+++ b/github.go
@@ -13,6 +13,8 @@ import (
 type GitHub interface {
 	ListReleases() ([]github.RepositoryRelease, error)
 	CreateRelease(release *github.RepositoryRelease) (*github.RepositoryRelease, error)
+
+	ListReleaseAssets(release *github.RepositoryRelease) ([]github.ReleaseAsset, error)
 	UploadReleaseAsset(release *github.RepositoryRelease, name string, file *os.File) error
 }
 
@@ -57,6 +59,15 @@ func (g *GitHubClient) CreateRelease(release *github.RepositoryRelease) (*github
 	return createdRelease, nil
 }
 
+func (g *GitHubClient) ListReleaseAssets(release *github.RepositoryRelease) ([]github.ReleaseAsset, error) {
+	assets, _, err := g.client.Repositories.ListReleaseAssets(g.user, g.repository, *release.ID, nil)
+	if err != nil {
+		return []github.ReleaseAsset{}, nil
+	}
+
+	return assets, nil
+}
+
 func (g *GitHubClient) UploadReleaseAsset(release *github.RepositoryRelease, name string, file *os.File) error {
 	_, _, err := g.client.Repositories.UploadReleaseAsset(
 		g.user,
diff --git a/in_command.go b/in_command.go
new file mode 100644
index 0000000..bdba78a
--- /dev/null
+++ b/in_command.go
@@ -0,0 +1,116 @@
+package resource
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"sort"
+
+	"github.com/google/go-github/github"
+)
+
+type InCommand struct {
+	github GitHub
+}
+
+func NewInCommand(github GitHub) *InCommand {
+	return &InCommand{
+		github: github,
+	}
+}
+
+func (c *InCommand) Run(destDir string, request InRequest) (InResponse, error) {
+	releases, err := c.github.ListReleases()
+	if err != nil {
+		return InResponse{}, nil
+	}
+
+	sort.Sort(byVersion(releases))
+
+	if len(releases) == 0 {
+		return InResponse{}, errors.New("no releases")
+	}
+
+	var foundRelease *github.RepositoryRelease
+
+	if request.Version == nil {
+		foundRelease = &releases[len(releases)-1]
+	} else {
+		for _, release := range releases {
+			if *release.TagName == request.Version.Tag {
+				foundRelease = &release
+				break
+			}
+		}
+	}
+
+	if foundRelease == nil {
+		return InResponse{}, fmt.Errorf("could not find release with tag: %s", request.Version.Tag)
+	}
+
+	assets, err := c.github.ListReleaseAssets(foundRelease)
+	if err != nil {
+		return InResponse{}, nil
+	}
+
+	for _, asset := range assets {
+		url := *asset.BrowserDownloadURL
+		path := filepath.Join(destDir, *asset.Name)
+
+		var matchFound bool
+		if len(request.Params.Globs) == 0 {
+			matchFound = true
+		} else {
+			for _, glob := range request.Params.Globs {
+				matches, err := filepath.Match(glob, *asset.Name)
+				if err != nil {
+					return InResponse{}, err
+				}
+
+				if matches {
+					matchFound = true
+					break
+				}
+			}
+		}
+
+		if !matchFound {
+			continue
+		}
+
+		err := c.downloadFile(url, path)
+		if err != nil {
+			return InResponse{}, nil
+		}
+	}
+
+	return InResponse{
+		Version: Version{
+			Tag: *foundRelease.TagName,
+		},
+	}, nil
+}
+
+func (c *InCommand) downloadFile(url, destPath string) error {
+	out, err := os.Create(destPath)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	resp, err := http.Get(url)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	_, err = io.Copy(out, resp.Body)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
diff --git a/in_command_test.go b/in_command_test.go
new file mode 100644
index 0000000..b984a3d
--- /dev/null
+++ b/in_command_test.go
@@ -0,0 +1,206 @@
+package resource_test
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"github.com/google/go-github/github"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	"github.com/onsi/gomega/ghttp"
+
+	"github.com/concourse/github-release-resource"
+	"github.com/concourse/github-release-resource/fakes"
+)
+
+var _ = Describe("In Command", func() {
+	var (
+		command      *resource.InCommand
+		githubClient *fakes.FakeGitHub
+		server       *ghttp.Server
+
+		inRequest resource.InRequest
+
+		inResponse resource.InResponse
+		inErr      error
+
+		destDir string
+	)
+
+	BeforeEach(func() {
+		var err error
+
+		githubClient = &fakes.FakeGitHub{}
+		command = resource.NewInCommand(githubClient)
+
+		destDir, err = ioutil.TempDir("", "github-release")
+		Ω(err).ShouldNot(HaveOccurred())
+
+		server = ghttp.NewServer()
+		server.RouteToHandler("GET", "/example.txt", ghttp.RespondWith(200, "example.txt"))
+		server.RouteToHandler("GET", "/example.rtf", ghttp.RespondWith(200, "example.rtf"))
+		server.RouteToHandler("GET", "/example.wtf", ghttp.RespondWith(200, "example.wtf"))
+
+		inRequest = resource.InRequest{}
+	})
+
+	JustBeforeEach(func() {
+		inResponse, inErr = command.Run(destDir, inRequest)
+	})
+
+	AfterEach(func() {
+		server.Close()
+		Ω(os.RemoveAll(destDir)).Should(Succeed())
+	})
+
+	buildRelease := func(id int, tag string) github.RepositoryRelease {
+		return github.RepositoryRelease{
+			ID:      &id,
+			TagName: &tag,
+		}
+	}
+
+	buildAsset := func(name string) github.ReleaseAsset {
+		url := server.URL() + "/" + name
+
+		return github.ReleaseAsset{
+			Name:               &name,
+			BrowserDownloadURL: &url,
+		}
+	}
+
+	Context("when there are releases", func() {
+		BeforeEach(func() {
+			githubClient.ListReleasesReturns([]github.RepositoryRelease{
+				buildRelease(2, "v0.35.0"),
+				buildRelease(1, "v0.34.0"),
+			}, nil)
+
+			githubClient.ListReleaseAssetsReturns([]github.ReleaseAsset{
+				buildAsset("example.txt"),
+				buildAsset("example.rtf"),
+				buildAsset("example.wtf"),
+			}, nil)
+		})
+
+		Context("when a present version is specified", func() {
+			BeforeEach(func() {
+				inRequest.Version = &resource.Version{
+					Tag: "v0.35.0",
+				}
+			})
+
+			Context("when valid asset filename globs are given", func() {
+				BeforeEach(func() {
+					inRequest.Params = resource.InParams{
+						Globs: []string{"*.txt", "*.rtf"},
+					}
+				})
+
+				It("succeeds", func() {
+					Ω(inErr).ShouldNot(HaveOccurred())
+				})
+
+				It("returns the fetched version", func() {
+					Ω(inResponse.Version).Should(Equal(resource.Version{Tag: "v0.35.0"}))
+				})
+
+				It("downloads only the files that match the globs", func() {
+					_, err := os.Stat(filepath.Join(destDir, "example.txt"))
+					Ω(err).ShouldNot(HaveOccurred())
+
+					_, err = os.Stat(filepath.Join(destDir, "example.rtf"))
+					Ω(err).ShouldNot(HaveOccurred())
+
+					_, err = os.Stat(filepath.Join(destDir, "example.wtf"))
+					Ω(err).Should(HaveOccurred())
+				})
+			})
+
+			Context("when an invalid asset filename glob is given", func() {
+				BeforeEach(func() {
+					inRequest.Params = resource.InParams{
+						Globs: []string{`[`},
+					}
+				})
+
+				It("returns an error", func() {
+					Ω(inErr).Should(HaveOccurred())
+				})
+			})
+
+			Context("when no globs are specified", func() {
+				BeforeEach(func() {
+					inRequest.Source = resource.Source{}
+				})
+
+				It("succeeds", func() {
+					Ω(inErr).ShouldNot(HaveOccurred())
+				})
+
+				It("returns the fetched version", func() {
+					Ω(inResponse.Version).Should(Equal(resource.Version{Tag: "v0.35.0"}))
+				})
+
+				It("downloads all of the files", func() {
+					_, err := os.Stat(filepath.Join(destDir, "example.txt"))
+					Ω(err).ShouldNot(HaveOccurred())
+
+					_, err = os.Stat(filepath.Join(destDir, "example.rtf"))
+					Ω(err).ShouldNot(HaveOccurred())
+
+					_, err = os.Stat(filepath.Join(destDir, "example.wtf"))
+					Ω(err).ShouldNot(HaveOccurred())
+				})
+			})
+		})
+
+		Context("when the specified version is not available", func() {
+			BeforeEach(func() {
+				inRequest.Version = &resource.Version{
+					Tag: "v0.36.0",
+				}
+			})
+
+			It("returns an error", func() {
+				Ω(inErr).Should(HaveOccurred())
+			})
+		})
+
+		Context("when the version is not specified", func() {
+			BeforeEach(func() {
+				inRequest.Version = nil
+			})
+
+			It("succeeds", func() {
+				Ω(inErr).ShouldNot(HaveOccurred())
+			})
+
+			It("returns the fetched version", func() {
+				Ω(inResponse.Version).Should(Equal(resource.Version{Tag: "v0.35.0"}))
+			})
+
+			It("fetches from the latest release", func() {
+				_, err := os.Stat(filepath.Join(destDir, "example.txt"))
+				Ω(err).ShouldNot(HaveOccurred())
+
+				_, err = os.Stat(filepath.Join(destDir, "example.rtf"))
+				Ω(err).ShouldNot(HaveOccurred())
+
+				_, err = os.Stat(filepath.Join(destDir, "example.wtf"))
+				Ω(err).ShouldNot(HaveOccurred())
+			})
+		})
+	})
+
+	Context("when no releases are present", func() {
+		BeforeEach(func() {
+			githubClient.ListReleasesReturns([]github.RepositoryRelease{}, nil)
+		})
+
+		It("returns an error", func() {
+			Ω(inErr).Should(HaveOccurred())
+		})
+	})
+})
diff --git a/resources.go b/resources.go
index f2da72f..3af0b8a 100644
--- a/resources.go
+++ b/resources.go
@@ -12,6 +12,21 @@ type CheckRequest struct {
 	Version Version `json:"version"`
 }
 
+type InRequest struct {
+	Source  Source   `json:"source"`
+	Version *Version `json:"version"`
+	Params  InParams `json:"params"`
+}
+
+type InParams struct {
+	Globs []string `json:"globs"`
+}
+
+type InResponse struct {
+	Version  Version        `json:"version"`
+	Metadata []MetadataPair `json:"metadata"`
+}
+
 type OutRequest struct {
 	Source Source    `json:"source"`
 	Params OutParams `json:"params"`
diff --git a/strings.go b/strings.go
new file mode 100644
index 0000000..fe9025f
--- /dev/null
+++ b/strings.go
@@ -0,0 +1,13 @@
+package resource
+
+import "unicode"
+
+func dropLeadingAlpha(s string) string {
+	for i, r := range s {
+		if !unicode.IsLetter(r) {
+			return s[i:]
+		}
+	}
+
+	return ""
+}