The prologue is set two years prior to the events of the main part of the game. You are controlling Ethan Mars at his home, with his wife and two boys. It's Jason's birthday (your older son), and you start off at home by yourself, waiting for your family to get home from the store. This chapter is essentially a tutorial, and it will teach you the basics on how to move and control your character. Don't worry about any impact on the plot; nothing you do here will have an effect on the story down the road.
You start out asleep in bed, and on-screen instructions will tell you to press to get up. From now on, when you see an arrow in a clear box with a white outline, just perform the movement indicated by the arrow. Repeat the action to stand up from bed. Before you get downstairs, you need to shower and get dressed. You can manipulate some of the objects in your room; just walk up to them until the instruction appears, and perform it.
Head to the door on the opposite side of the room and pick up the note on the floor. After learning that your wife and kids are out on errands, put the note down and exit the room. When you get out into the hall you'll be prompted to use to listen to Ethan's thoughts. Use this button any time, with any character to hear what they're thinking. When you see the possible thoughts, press the controller button that corresponds with the option. Hold and press to think about taking a shower.
The bathroom is right next to the master bedroom. You also have the option to go explore things in the hall and your kids' room, or brush your teeth in the bathroom. When you're ready, head around the short wall in the bathroom to the shower. Take off your clothes and get in the shower, then dry yourself off afterwards by shaking the controller up and down, then side to side. Head back into your room and put on the clothes you'll find in your closet.
When you're all dressed, you can head down the stairs at the end of the hall. There are lots of things to do downstairs, and you can listen to Ethan's thoughts for some ideas. You'll have a set amount of time to accomplish whatever you want to do before your wife gets back. For the Happy Birthday trophy, you'll want to finish your work. Head to the opposite end of the house from the kitchen, and go up into the back room to the left of the sliding glass door. Sit down at the chair to begin drafting the plans.
At your drafting table you'll see an instruction to press . Each time you do, you'll pick up another drawing instrument and do some work on the plans. Each thing you do will teach you about the different types of instructions you may see throughout the game. Keep doing the actions to learn about doing normal instructions, combo instructions, timed instructions and shaking the controller. You'll need to keep working at your desk until you sign the finished product to count toward the trophy. When you're done, mess around inside or out in the yard until your family gets home.
Grab the groceries from your wife using combo instructions, and don't let go before you set them down on the counter. After your wife asks you how your work went, she'll want you to set the table for her. This is a required action for the trophy, so press to answer both her queries, then head over to the low cabinet next to the table. Once you get the cabinet open and take out the plates, carefully set them down on the table. If you're not playing on the easiest difficulty, you'll be introduced to slowly unfolding instructions. These look like normal instructions, except the white border is dashed. Perform the actions slowly so you don't drop any dishes.
Now that you're done helping your wife set up for Jason's party, go outside to where the boys are playing. Playing with your kids is the last requirement for the Happy Birthday trophy, and it's important that you keep going until the game stops you. First you'll pick between Jason and Shaun for who you'll play with first, and you can choose either one. You give Jason a helicopter ride, then put Shaun up on your shoulders and run around your yard. You can control your direction by tilting the controller. When you get back to where Jason is, you'll see an instruction for putting Shaun down, but don't do it if you want the trophy. Just keep running around until Ethan puts him down on his own.
Next you'll pick up both kids at once by quickly tapping . That's followed by the swordfight with Jason. This is a series of timed button presses, and you can either win the fight or let your kid win. Once your wife calls you back inside for lunch, the games will over and you should get the trophy at the next load screen. Go inside, then back upstairs to find Shaun. At the top of the stairs you'll see him by the birdcage. Going over and kneeling down by him is the last action of the chapter.