Blood on the Tracks (S04E15)

Lilly investigates the deaths of a married couple who perished in 1981 when a supposedly accidental gas-leak explosion set their house on fire. The case is reopened when fragments of a bomb are discovered at the house during renovations. The investigation reveals the victims were involved in violent antiwar activities during the Vietnam War. Back at headquarters, Stillman takes care of his 4-year-old grandson. (CBS TV Network)