Episode 508, "Forget Oblivion"
SEASON 4, EPISODE 416 - When Samís sister Natalie is threatened by her drug-running ex-boyfriend, Natalie turns to Spike for help. Without telling Sam, Spike steps up to protect her Ė and winds up in a trap that will force him to recover stolen heroin from a highly secure evidence depot. At the same time, he must square off against an even more dangerous foe: his own team. Putting the many losses (Lou, Oliver and his father), he has sustained recently, Spike deftly wins the confidence of the villains as he jams security frequencies, while simultaneously signaling the SRU where to rescue Natalie and himself.