Just a couple plot questions... [spoilers]

[Bob Saget]

Okay, so I've just played through Overture and Black Plague these past few weeks, and I just have a few questions.

1:

Spoiler below!

Why did the scientist that you gave the saw to try to kill you?

2:

Spoiler below!

What was the thing in the walls in The Kennels?

3:

Spoiler below!

If Phillip and Red were infected, how come they didn't become zombies, like everyone else?

Anyway, that's about all for now, until I come up with some more. Thanks in advance for answering them.