Beat the game as Keith to unlock another game where you play as the heroine, Skye. Beat Skye's game to unlock Challenge mode.
Raft Escape tips:
To escape on the raft, you have to realize it's usable (approach it!), bring Skye with you, and have swiped the flare from the enemy hideout. When you see a ship on the way home, shoot the flare. If you forgot it, guess what? The ship won't see you, and you and your baby starve to death. Be prepared!
Thanks to Revolution Readers Huntergather and StiK!