catch somebody red-handed
catch somebody in the act

What if someone came along and caught them in the act?

She'd caught him in the act of getting ready for bed.

I will just have to catch her in the act!

Anyone who caught him in the act was quick indeed.

He and his friends had been caught in the act.

To catch history in the act of moving forward again.

The next time, he was caught in the very act of running away.

Half an hour earlier, and we would have caught him in the act.

Why on earth wait to catch him in the act?

So far, he had never been caught in the act.