diff --git a/src/SubFix.hs b/src/SubFix.hs
index c36c50b..344ecc0 100644
--- a/src/SubFix.hs
+++ b/src/SubFix.hs
@@ -20,6 +20,8 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 -}
 
+{-# LANGUAGE LambdaCase, RecordWildCards #-}
+
 module SubFix (
   -- * Data Types
   Caption (..),
@@ -29,8 +31,12 @@ module SubFix (
   encode,
 ) where
 
+import Control.Monad.Trans.Class (lift)
+import Control.Monad.Trans.State (StateT, evalStateT, get, put)
 import Data.Char (chr)
 
+import SubFix.Internal (decodeTime)
+
 -- | Defines a caption group
 data Caption = Caption
   { capID :: Int
@@ -54,7 +60,7 @@ decode
   -> Either String [Caption]
   -- ^ The resulting caption list, or a message describing the error
   -- that occured.
-decode = undefined
+decode = evalStateT decodeLoop . lines
 
 -- | Encodes a list of caption groups
 encode :: [Caption] -> String
@@ -72,4 +78,58 @@ checkNotes "" = ""
 checkNotes ('#' : '#' : str) = chr 0x2669 : checkNotes str
 checkNotes (ch : str) = ch : checkNotes str
 
+decodeLoop :: StateT [String] (Either String) [Caption]
+decodeLoop = get >>= \case
+  [] -> return []
+  _  -> do
+    caption  <- decodeNextCaption
+    captions <- decodeLoop
+    return $ caption : captions
+
+decodeNextCaption :: StateT [String] (Either String) Caption
+decodeNextCaption = do
+  capID              <- decodeID
+  (capStart, capEnd) <- decodeTimes
+  capText            <- decodeText
+  return $ Caption {..}
+
+decodeID :: StateT [String] (Either String) Int
+decodeID = do
+  line <- nextLine
+  case reads line of
+    [(val, "")] -> return val
+    _           -> lift $ Left "invalid caption ID"
+
+decodeTimes :: StateT [String] (Either String) (Integer, Integer)
+decodeTimes = do
+  line <- nextLine
+  case words line of
+    [startStr, "-->", endStr] -> do
+      start <- case decodeTime startStr of
+        Just (val, "") -> return val
+        _              -> lift $ Left "invalid start time"
+      end <- case decodeTime endStr of
+        Just (val, "") -> return val
+        _              -> lift $ Left "invalid end time"
+      return (start, end)
+    _ -> lift $ Left "invalid time signature"
+
+decodeText :: StateT [String] (Either String) String
+decodeText = get >>= \case
+  [] -> return ""
+  _  -> do
+    line <- nextLine
+    if line == ""
+      then return ""
+      else do
+        next <- decodeText
+        return $ line ++ "\n" ++ next
+
+nextLine :: StateT [String] (Either String) String
+nextLine = get >>= \case
+  (line : remaining) -> do
+    put remaining
+    return line
+  [] -> lift $ Left "missing line"
+
 --jl
diff --git a/subfix.cabal b/subfix.cabal
index de55d88..f97865e 100644
--- a/subfix.cabal
+++ b/subfix.cabal
@@ -4,7 +4,7 @@ cabal-version: 1.12
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 475ccf2c735b96ddd94fc9281d9e8e97ecf64c4b60cd6645112a6ffb72165873
+-- hash: ce33ad286b77569617c489030c5bec8597e68ad69f7a34c12d95ad54614a59f2
 
 name:           subfix
 version:        0.0.0
@@ -58,6 +58,7 @@ test-suite subfix-test
   main-is: Spec.hs
   other-modules:
       SubFix.ConvertSpec
+      SubFix.DecodeSpec
       SubFix.Internal.DecodeTimeSpec
       SubFix.Internal.TimestampSpec
       SubFix.InternalSpec
diff --git a/test/SubFix/DecodeSpec.hs b/test/SubFix/DecodeSpec.hs
new file mode 100644
index 0000000..87c922c
--- /dev/null
+++ b/test/SubFix/DecodeSpec.hs
@@ -0,0 +1,160 @@
+{-
+
+subfix
+Copyright (C) Jonathan Lamothe <jonathan@jlamothe.net>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at
+your option) any later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+-}
+
+module SubFix.DecodeSpec (spec) where
+
+import Test.Hspec (Spec, context, describe, it, shouldBe)
+
+import SubFix (Caption (..), decode)
+import SubFix.Internal (timestamp)
+
+spec :: Spec
+spec = describe "decode" $ do
+  context "valid inputs" $ mapM_
+    ( \(label, input, expected) ->
+      context label $ do
+        let Right results = decode input
+
+        context "number of results" $ let
+          rlen = length results
+          elen = length expected
+          in it ("should be " ++ show elen) $
+            rlen `shouldBe` elen
+
+        mapM_
+          ( \(num, r, e) ->
+            context ("result #" ++ show num) $
+              it ("should be " ++ show e) $
+                r `shouldBe` e
+          ) $ zip3 [(1::Int)..] results expected
+    )
+
+    --  label,            input,         expected
+    [ ( "empty",          "",            []             )
+    , ( "one caption",    oneCaption,    oneCaption'    )
+    , ( "two captions",   twoCaptions,   twoCaptions'   )
+    , ( "three captions", threeCaptions, threeCaptions' )
+    , ( "multi-line",     multiLine,     multiLine'     )
+    ]
+
+  context "invalid inputs" $ mapM_
+    ( \(label, input, expected) ->
+      context label $ let
+        Left result = decode input
+        in it ("should be: " ++ expected) $
+          result `shouldBe` expected
+    )
+
+    --  label,            input,    expected
+    [ ( "bad ID",         badID,    badID'    )
+    , ( "bad start time", badStart, badStart' )
+    , ( "bad end time",   badEnd,   badEnd'   )
+    , ( "bad separator",  badSep,   badSep'   )
+    ]
+
+  where
+    oneCaption = unlines
+      [ "1"
+      , "01:02:03,004 --> 05:06:07,008"
+      , "foo"
+      ]
+
+    oneCaption' =
+      [ Caption
+        { capID    = 1
+        , capStart = timestamp 1 2 3 4
+        , capEnd   = timestamp 5 6 7 8
+        , capText  = "foo\n"
+        }
+      ]
+
+    twoCaptions = oneCaption ++ unlines
+      [ ""
+      , "2"
+      , "09:10:11,012 --> 13:14:15,016"
+      , "bar"
+      ]
+
+    twoCaptions' = oneCaption' ++
+      [ Caption
+        { capID    = 2
+        , capStart = timestamp 9 10 11 12
+        , capEnd   = timestamp 13 14 15 16
+        , capText  = "bar\n"
+        }
+      ]
+
+    threeCaptions = twoCaptions ++ unlines
+      [ ""
+      , "3"
+      , "17:18:19,020 --> 21:22:23,024"
+      , "baz"
+      ]
+
+    threeCaptions' = twoCaptions' ++
+      [ Caption
+        { capID    = 3
+        , capStart = timestamp 17 18 19 20
+        , capEnd   = timestamp 21 22 23 24
+        , capText  = "baz\n"
+        }
+      ]
+
+    multiLine = unlines
+      [ "1"
+      , "01:02:03,004 --> 05:06:07,008"
+      , "foo"
+      , "bar"
+      ]
+
+    multiLine' =
+      [ Caption
+        { capID    = 1
+        , capStart = timestamp 1 2 3 4
+        , capEnd   = timestamp 5 6 7 8
+        , capText  = "foo\nbar\n"
+        }
+      ]
+
+    badID  = "asdf"
+    badID' = "invalid caption ID"
+
+    badStart = unlines
+      [ "1"
+      , "asdf --> 01:02:03,004"
+      ]
+
+    badStart' = "invalid start time"
+
+    badEnd = unlines
+      [ "1"
+      , "01:02:03,004 --> asdf"
+      ]
+
+    badEnd' = "invalid end time"
+
+    badSep = unlines
+      [ "1"
+      , "01:02:03,004 asdf 05:06:07,008"
+      ]
+
+    badSep' = "invalid time signature"
+
+--jl
diff --git a/test/SubFixSpec.hs b/test/SubFixSpec.hs
index 7a30e16..ffb3b65 100644
--- a/test/SubFixSpec.hs
+++ b/test/SubFixSpec.hs
@@ -23,12 +23,13 @@ module SubFixSpec (spec) where
 import Test.Hspec (Spec, describe)
 
 import qualified SubFix.InternalSpec as Internal
-
+import qualified SubFix.DecodeSpec as Decode
 import qualified SubFix.ConvertSpec as Convert
 
 spec :: Spec
 spec = describe "SubFix" $ do
   Internal.spec
+  Decode.spec
   Convert.spec
 
 --jl