How did the police find Frank?

In the movie Labor Day (2013), Adele, Frank and Henry were just about to get in the car and leave when the police showed up and took Frank away. My question is how did the police know where Frank was? There are possible solutions, but each has its own problem

1. The neighbor, Evelyn, came over and found Frank in the house and they had a conversation about him being the handyman. In the book, Evelyn believes Frank's story and moves on. She did looked worried/suspicious, but may have been from the shock of seeing an empty house.

2. Eleanor guessed that the man Henry was telling her about was Frank. In the book, Henry tells Eleanor all about it and she turns in Frank for the reward money to go to a private school. But in the movie, she didn't seem too interested in the fact that it was Frank and for all we know did know about the reward.

3. Henry told his dad or gave some kind of clue in his note. We don't know what was in the note however, but Henry did act a bit strange when he got back to the house and didn't seem concerned when they heard sirens. But, if that was his intention, why didn't he just tell the cop that picked him up on his way back home from dropping off the note?

4. The cop that dropped off Henry realized something was off and may have gotten suspicious due to Adele's behavior. But there were not signs as to this being what happened.

So, how did the cops know where to find Frank?