1. The next important event occurs at 10:00 AM on the 22nd. If you have plenty of time before then, this is a good time to work on the Hella Copter achievement. Position yourself as shown here then jump onto the roof of this shelter in Leisure Park to avoid zombies.
2. Bring several Machine Guns with you. Anticipate where the chopper will be right after it passes overhead then shoot its vulnerable tail section. A few well-placed shots is all it takes to earn the achievement. The shot above was taken just as I got the Hella Copter achievement.
3. If you've completed all the Cases and want Ending A (which unlocks the ability to play Overtime), you'll need to be in Carlito's Hideout between 10:00 AM and 12:00 Noon on the 22nd.
4. You'll witness this cutscene of special forces wiping out the mall rats.
5. The cutscene closes with a close-up of this mysterious figure. Hmm - wonder if we'll see him again?
6. After the cutscene, talk to Isabela and she tells you to save yourself. Time to get to the heliport.
7. You'll have a clear run back to the security office. The military has cleared out the zombies, and the troops all seem to be at brunch.
8. It's been a while since you've been to the Heliport -- you're forgiven if you forget how to get there. From the security office hallway, ascend the stairs to this door.
9. To get Ending A, make sure you stand on the helipad itself. I always stand on the "H" just to play it safe. Now you need to patiently wait until 12:00 Noon.
10. None of the endings are very cheerful, but Ending A is particularly heartbreaking. At first, Frank is convinced the chopper isn't coming. Then, after great relief at seeing the chopper approaching, the pilot becomes zombie chow. Didn't your mother warn you to check the back seat before getting in?
11. The cutscene concludes with Frank on the newly-zombified roof.
12. After the ending credits, you'll be presented with your results screen. Here's the results from my third run, from which most of this walkthrough was derived. Those who clear Ending A are now free to proceed to Overtime.
13. If you fail any of the Cases but are at the helipad by noon on the 22nd, you'll see Ending B. I also received this ending regardless of where I was if I failed to talk to Isabela as she waited for me on the roof during Case 8.
14. Otis and Jessie are saved, along with any survivors you may have rescued.
15. This good fortune is short-lived, as cities all across America fall victim to similar zombie outbreaks.
16. Now for Ending C. If you succeed at all of the Cases but fail to be at the Helipad by Noon, or fail to report to Isabela in Carlito's Hideout between 10:00 AM and Noon, this is your ending.
17. Your pilot meets the same fate as in Ending A, but this time he's on the ground.
18. Willamette is doomed, but at least the infection doesn't spread outside the city.
19. Ending D begins with your capture by the Special Forces. Lose your last bit of health to one of these guys and you'll become their captive.
20. You'll be stripped and bound, and will be beaten if the troops see you trying to escape. Wait until their backs are turned then rock the left stick back and forth, just like when you try to break free from a zombie. Repeat until the yellow bar is full.
21. If you are successful, you'll find yourself in the alley that leads to the Maintenance Tunnels.
22. If you are unsuccessful, you'll get Ending D. The message which follows the one above: "However, the true story of what had occurred there remains unreported to this day..."
23. Ending E is similar to Ending B, but in addition to failing to finish all Cases, you also fail to be on the helipad by noon on the 22nd.
24. Jessie, Otis, and the other survivors are rescued...
25. ...but Frank is nowhere to be found.
26. Ending F is shown if you fail to stop all of Carlito's bombs in Case 7.