All he could think was that the police would knock on his door at any moment.

About 15 minutes later the police were knocking on his wife's door.

Now the police were knocking on doors, in a building that itself was a crime.

Because a few hours later, the police were knocking at her door.

Residents said that the police had knocked on their doors early yesterday, seeking information.

Assuming that the police do knock and announce their presence, what happens next?

Neither of us need fear a police knock on the door to question our motives.

"It seems the police always knock, at least when they come to my house," I said.

i found out when the police knocked on my door in the middle of the night.

The police knocked and asked Charles if they could search, which he refused.