The "heavy" in this episode is a crooked federal narcotics agent. Enjoying a brisk sideline of peddling dope during his off-hours, the agent commits murder when one of his customers discovers his true identity. Meanwhile, undercover cop Tony Baretta (Robert Blake) tries to root out the rotten apple in the law-enforcement barrel. Originally slated to air on January 5, 1977, "Don't Kill the Sparrow" was bumped forward to January 12. ~ Hal Erickson, Rovi