The Sentinel (1996) 2x17

A birthday party for Katrina, a young Russian woman, is interrupted by a vicious attack that claims the life of two men and ends with the theft of a mysterious black suitcase from the woman's boyfriend, Sergei. Ellison and Sandburg receive little cooperation from the witnesses, but Ellison's "Sentinel" intuition leads him to discover a gold neckchain worn by Sergei is, in fact, radioactive.