Episode 4

S5 E4: When a young man is found dead and stark naked out on the Fens, Will and Geordie discover ties to a Cambridge research project experimenting with mind altering drugs. Their arrogant Professor is a proponent of the 'wonder drug' LSD in his psychotherapy sessions, but Will and Geordie quickly start wondering whether there is more going on. As the case gets murkier, Will's own feelings of guilt about his father's death and his conflicted feelings about Ellie start to take their toll. Is he prepared to delve deep within himself to find the answers? Meanwhile, the Keatings face one of their toughest decisions yet, after a catastrophically awkward dinner party leaves more than just the baked Alaska burnt around the edges. Will Cathy finally tell Geordie the truth about her mother? And with the Chapman feud showing no sign of relenting, Leonard must try to convince Mrs C that there's good in the world, but will the most wilful woman in the parish ever come round?