A subway station gas attack, similar to one that took place in a Baltimore church five years earlier, brings Baltimore homicide detectives Tim Bayliss and Frank Pembleton to New York to assist Briscoe and Curtis in apprehending the prime suspect in both incidents. (Part 1 of a crossover event with 'For God and Country (2)' Homicide: Life on the Street, season 4, episode 12.) (thetvdb.com)