Russian immigrant Sergei Vetotchkin can't understand why his teenage son was shot in his ice cream vending van at night, way off his route. Ryan and Esposito soon find that he had mysterious business using a shared postal locker with a retired cop who is also found fatally shot, as was their common friend, Russian Dmitri. A parental permission slip found in the ice cream van convinces the police that one of the students in the class must have witnessed the murder. So Castle is assigned to the class of over-protective teacher Leslie Ruiz, to win the kids' confidence. But each one who confides to him has nothing to do with the murder. Finally, Beckett and Castle work out what each victim's home was searched for and where the precious clue is.
—KGF Vissers