Oxford professor and amateur stargazer Andrew Crompton emerges from a church confessional, cryptically exclaiming that on Friday at 3:15, he’ll have an “excess of joy.” Later, Crompton is found dead at the foot of the stairs in the Oxford observatory. The investigation draws Detective Inspector Lewis (Kevin Whately) and Detective Sergeant Hathaway (Laurence Fox) into the ethereal writings of a 17th-century astronomer and a modern-day circle of scientists and musicians, and their unexpected connections to the deceased.