The player is first introduced to Ethan Mars, the main character/protagonist of the game. Ethan is an architect who is married to Grace Mars and is the father of two boys, Jason Mars and Shaun Mars. This chapter serves two purposes: one, to be a gameplay tutorial; and two, to explain the basic premise of the storyline (before the story really starts in the next chapter).
This chapter is also meant to show Ethan's relationship with his sons before future events.
Players can be as thorough or as cursory as they wish whilst guiding Ethan around the home. Keen players can engage Ethan in many activities, including brushing his teeth, showering, playing a radio, finishing an architectural concept drawing (required for the trophy of this chapter), playing with a remote control car, drinking coffee and orange juice, and getting dressed, whilst less enthusiastic players can simply await the return of Ethan's wife, Grace, and his two sons Shaun and Jason. The player's level of involvement in the activities available has no visible effect on the story.
Once Grace and the boys arrive, it is up to the player to prepare for Jason's birthday by setting the table (which is required to earn a trophy). Afterward, the player can engage with Grace in a romantic moment and play with Jason and Shaun in the backyard.
The chapter ends when Grace calls the family to the table to eat lunch, only to discover that Shaun is missing. The player must guide Ethan upstairs to find Shaun huddled over Merlin, the family's pet who has died (quite recently, as it was singing and healthy when Ethan first awoke). Ethan attempts to comfort him and the chapter ends.
- Ethan Mars - Playable character.
- Shaun Mars - Ethan's son and younger brother of Jason Mars.
- Jason Mars - Ethan's other son who is turning ten in the chapter.
- Grace Mars - Ethan's wife and the mother of Jason and Shaun.
- Happy Birthday: Prologue - Complete the drawing + Set the table + Play with the kids (Bronze)
- Interactive Drama: Thank you for supporting Interactive Drama (Bronze)
- Grace's note to Ethan says she will pick up the kids from school, while a few moments earlier it is noted that it's a Saturday. This may be explained by the fact that Quantic Dream is a French studio. French pupils in primary and high schools are used to working on Saturday mornings. (Note that Shaun and Jason have the afternoon free.)
- There is evidence that shows that players would be shown a full-frontal view of Ethan's shower scene. This was likely removed due to censorship. However, there are image stills online that state the full, uncensored cutscene may be obtainable via glitching.
- This chapter has the first shower scene in the game.
- This is the first and only chapter to feature a pet.
- Grace and Ethan will have a humorous conversation if he plays with the remote controlled toy car while she is in the kitchen.
- Grace: "I thought that was for the kids."
- Ethan: "Oh, I'm just... checking if it works."
- Grace: "Right..."
- During Ethan's shower scene, an apparent glitch exposes Ethan's genitalia, which is usually cut off.
Chapters played as Ethan (in chronological order) - Prologue | The Mall | Father and Son | The Shrink | The Park | Where's Shaun? | Paparazzi | Lexington Station | The Motel | The Bear | The Butterfly | The Lizard | Fugitive | The Shark | On the Loose | The Rat | The Old Warehouse
Chapters played as Scott (in chronological order) - Sleazy Place | Hassan's Shop | Suicide Baby | A Visitor | Kramer's Party | The Golf Club | Manfred | Eureka | The Cemetery | Flowers on the Grave | Trapped | Face to Face | Hold My Hand | Origami Killer
Chapters played as Norman (in chronological order) - Crime Scene | Welcome, Norman | Kick Off Meeting | Nathaniel | Covered Market | Shrink and Punches | Jayden Blues | Under Arrest | Mad Jack | Fish Tank | Solving the Puzzle | The Old Warehouse