Cold Case: Blood on the Tracks / Season: 4 / Episode: 15 (2007)

When remnants of a bomb are found during remodeling of an old house, the team reopens the case of a married couple who died there in 1981, in what was thought to be an accidental gas leak. 
 
Lilly sees one of the victims in the case room while the other victim is seen looking in a patrol car's window when the killer is arrested.