Instructions
Complete all of the case files in "Dead Rising." The game has eight story-related cases that escalate in complexity and difficulty as the game progresses. You begin the first case shortly after entering the mall when you complete the game's prologue. These cases make up the bulk of the Story mode in the game, and you only have three days to complete them all.
Watch the Special Forces' arrival cutscene. The Special Forces arrive at midnight on the third day, shortly after you find the zombified Jessie and are making your way back to Carlito's Hideout.
Go to Carlito's Hideout by 10 a.m. on Day 3. The Special Forces will hunt you after they arrive. If they capture you, they will hold you in captivity. Attack them if you want while time passes, but make sure you're back at the hideout to talk to Isabella when the Special Forces leave the mall at 10 a.m.
Go to the heliport by noon on Day 3. Doing so triggers the final cutscene in the game. However, if you have accomplished all of the required tasks to get the true ending, the game unlocks Overtime mode after the credits roll.
Complete the game in Overtime mode. This mode sees you running around the mall collecting supplies that will prevent you from turning into a zombie yourself, while avoiding the Special Forces, who have returned. Beat this extra chapter in the game to view the true ending for "Dead Rising."