The Tarot Card killer is caught by the police, and owns up to the murders.
Sondra goes to Peter's holiday home for a romantic weekend, assuming now that he is completely innocent. Sid is not convinced, and is still hung up on the envelope-clue that he found in Peter's house addressed to 'Betty G' - the name of the last prostitute who was murdered.
Peter owns up to Sondra that he was in London on the day he was meant to be out of the country, but it was for a top-secret business meeting. Sondra laughs it off, and all is good.
Sid returns to Peter's house, and lies to get past the housekeeper and uses the same code to get inside the secret music room again. This time under the French horn is a key (I know, after hiding the cards there before, you think he would find a better hiding place). Sid is caught by the housekeeper, and quickly leaves. The housekeeper phones Peter to warn him.
Sid also calls Sondra to warn her. Peter listens in to the conversation from another room. Sid tells her that he is going to check if the key opens the apartment. Sondra doesn't believe him.
Peter takes Sondra out to the lake on a row boat.
Sid makes it to Betty's apartment -- and the key fits! He gets into his little car and races over to save Sondra, terrified behind the wheel.
On the lake, Peter confesses that he knew Betty G -- she was a prostitute that he visited, and she blackmailed him. When he saw that there was a killer on the loose, he grabbed his chance and decided to frame him for her murder. He then wrestles with Sondra and pushes her overboard. As she goes under the water he rows back and kicks away the boat.
After drying himself, he phones the police to report the accident - that he thinks Sondra may have drowned.
The police show up -- but so does Sondra, still wet. As it turns out, she was a champion swimmer back at school. The game is up, and Peter is arrested.
Meanwhile, Sid didn't make it. He crashed on the way to rescue Sondra, and is on the Grim Reaper's ferry, where he starts to do his magic trick routine again to the other passengers.