stop someone in their tracks
stop (someone or something) (dead) in its/(one's) tracks
To make someone or something stop or come to a complete halt immediately or very suddenly. Hearing the gunshot in the distance stopped us both dead in our tracks. Boy, Samantha could stop you in her tracks with her smile!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
stop someone in their tracksor
stop someone dead in their tracks
COMMON If something stops you in your tracks or stops you dead in your tracks, it makes you suddenly stop what you are doing because you are very surprised or frightened. Seen across wide fields of corn this magnificent church cannot fail to stop you in your tracks. Note: You can also say that someone stops in their tracks or stops dead in their tracks. They stopped in their tracks and stared at him in amazement. They turned round. And then they stopped dead in their tracks, their hearts beating fast. Somebody was behind them.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012