behind somebody's back

She was out with a couple of men behind my back.

Only because you don't know what I say behind your back.

You went behind my back and took her away from me.

But over all always felt like i had to look behind my back.

He had set the whole thing up behind my back.

"You had no right going behind my back to him without ever saying a word to me."

Then one of the hands started to move behind the woman's back.

The rest of you, face down on the floor, hands behind your back.

Things they told you about behind the back of the hand.

None of us need ever go behind my father's back.