dead in (someone's or something's) tracks
In the exact spot or instant in which someone or something is. The phrase refers to instantly stopping and remaining motionless, silent, and/or inactive upon encountering something. The sound of leaking water stopped me dead in my tracks, and I cringed at the thought of yet another home repair. Even though we were talking quietly, the noise stopped the deer dead in its tracks.
dead in one's tracks
see under stop cold.