In the movie Panic Room how did the police know to come back?

It has been a few years but the police officer could tell something was wrong, her mannerisms and body language were all off.
He asked her several times about any issues, the fact that she would not say anything told him that there was a serious issue - hence he made sure that the police came back mob-handed.

The script indicates that her body language is all over the place and the whole scene just looks wrong.

• She didn't invite them in despite mentioning that it's freezing cold. She then shuts the interior door which would make it colder, not warmer.

• She's covered in dirt, despite the exterior of the house being immaculate

• She didn't cross her heart when she said "Cross my heart"

• The cop asks her if she can speak and she immediately mentions "if somebody was in the house or something?"

Cop 1 studies her, notices the burned sleeve of her T-shirt, the black smudges still on her face.

and

MEG: Man, you are good! You mean, like, if somebody was in the house or something? That's great, they really train you guys these days, don't they?

Cop 1 looks at her, not sure if he believes her or not.

MEG: No. I'm fine. Cross my heart.

later

It's the Cop, the first Cop, the one who came to the door and was so suspicious of Meg. The Cop looks down, sees blood smeared all over Burnham's jacket, sees more than enough to know his suspicions were correct.

In the movie, the cop tells her something along the lines of "if you're in some type of danger that you can't really talk about right now, you can use a signal or something -- like maybe blink a couple of times." Throughout the whole time he talks, it is clear that he does not blink (a signal) and neither does Meg. And so, him not blinking was a signal to Meg to actually NOT blink if something was wrong. Or maybe he's just good at body language.

When Officer Keeney asked Meg to give him a signal, she does not, but she does respond with "You guys are good, they really do train you guys." This is saying something IS wrong and because of your training, you have picked up on it.

I think there were more than a few shots: the robbers beat up Stephen, Meg used a sledgehammer to smash cameras and knock Raoul down the stairs. So the neighbors might have complained of the noise again.

Also, the police might have tried to check again later with Stephen, or his new wife might have called the police. The new wife would tell them that he went over to Meg's house and never came back.

It doesn't seem very realistic to me that the police would respond with such attention and force, but it is a rich neighborhood.

Do you remember when the mom called her husband? She was like (I don't know the exact words but something like this) "they were 3 men in the house" blah, blah. And a little more information before the line was cut. When the police officer asked her "what was the end of the sentence", she said that there are three things she would do if you come and jump on the bed with her right now. And she said she hung up before she says those things -- WHICH IS A LIE that the cop knew. He grew more suspicious because the line wasn't cut right there.

And like the comment above, on how he didn't blink and the mom didn't blink too, I think that was one too. And maybe of course it was too obvious that the mom is acting sooooooo strange.

Well, the lead officer the way that he kept looking at her throughout the conversation, I think he always knew something was wrong because of the previous 911 calls and the odd way she was acting. Also, after he told her about the blinking twice, she said something about if there was someone in the house or something? And then a moment later ran her hand through her hair, which I always was supposed to be a clue to the officer.

The cop tells her to make a sign like blink her eyes or something along the lines of that. She then responds, "oh like if someone had broken in" (hint1) then says "no I'm fine" as she brushes her hair from her face (her way of blinking). She couldn't blink her eyes because she knew they were watching and didn't know if the robbers could hear.

I think it's when the cop asked her to finish that sentence "there are three..." she intentionally gave the wrong answer. She told Stephan "there are three men upstairs“ before getting cut off so Stephan must have told the police the same thing.

I just saw the movie for the second time. I think the answer is pretty simple. She told her ex husband "Stephen, there are three men, they broke into the house". This had to be relayed to the police when Stephen called. The officer had to know this. When she did not answer that question correctly to the officer, that's when the officer knew something was wrong.

Another thing to consider, she called 911. 911 calls automatically get a police response, whether the call is completed or not. That is one of the advantages of the 911 system, that you can call for help if your house is on fire, and not have to stick around to give an address. So the police dispatcher had two calls regarding the same address, her initial call and Stephens call. That should key the officer into the fact that there was something awry.

I just got through watching it again, and here's my take on why the cops came back. The Dad called the cops, and also came over. Mom said everything was fine, and the cops left. Here's where the answer lies. The cops would have called the Dad back to inform him that everything was alright. Obviously, the girlfriend would have answered, and explained that he went over there and that he was really worried. The cops would have now known that the Mom was lying, that the Dad was there, and that something was going on. The other thought I had was maybe the Dad drove over there, and the cops ran the plates on his car and started connecting the dots.