Hot on somebody’s/something’stracks/trail
Definition 1 of 2
Pro Tip 1/3Urgency Implied
This phrase often indicates a sense of urgency and immediate action in pursuing someone. 
Detectives are hot on the thief's trail, searching every possible hideout.
Pro Tip 2/3Not Literal
The phrase is usually used metaphorically, not meaning someone is physically close behind. 
The competition is hot on our tracks with their new product release.
Pro Tip 3/3Determined Pursuit
It conveys the pursuer's determination to follow the lead until the end. 
The journalist was hot on the trail of the scandal, revealing truths at every turn.