Landis makes no sense.
I know he doesn't necessarily have to.. it's just that there don't appear to be ANY motives that are consistent with his character. Almost every part of his behavior creates questions.
(SPOILERS BELOW)
The babysitter is called in at the last second, and yet she is targeted by the psychopath. This raises the following questions:
1. How did he find her?
2. Why did he pick her?
3. Was he targeting her or was he targeting the family?
4. For what reason does he take the kids when his goal was to attack/kill the babysitter?
5. If his goal WAS to take the kids then why risk alerting the babysitter? 6. Especially when taking the children was so incredibly easy?
7. If his goal was the kids, then why does he hunt down Jill later on?
9. If his goal was Jill, why does he keep the kids alive for a few years before killing them (or refer back to the original question, why take the kids at all?)
10. If he DID want to take the kids, for what reason?
11. If he DID take the kids for any reason, why kill them later rather than sooner?
12. If the goal (as another poster suggested) was to kill the kids to prove that they were not safe in a nice house with lots of money, WHY take them at all when killing them works better?
And after he finds Jill again:
1. Why hunt her down to tell her that the kids are dead? She's not the mother and he KNOWS that.
2. What does he want from Jill and why can't he just take it? It's obvious that getting to her is a simple enough task.
Aww I have more questions but screw it, you get the idea. The reasoning behind the antagonist in this movie is screwy to say the least. It didn't scare me, just made me angry as all hell.