MacMillan's investigation of a suspicious burglary finds him crossing paths (and swords) with a number of his and Sally's friends. Mac, Sally and Sgt. Enright go undercover to a costume ball, where Mac is confident the culprit will strike.
The McMillans befriend Billy Benton, quarterback for the Hawks, who is either innocent or involved in a plot to throw the game. A $75,000 bet was made against the Hawks, and the bettor intends to collect at any cost, even murder.
Mac's ex-pug pal Freddie O'Neale becomes a target for murder after he claims he can identify The Dutchman, a notorious jewel thief whose face is unknown to the police and to the posh San Francisco social set whose treasures he plunders.
It's Sally's birthday, but she and Mac are in no mood to celebrate as someone has broken into their house and stolen all the sharp objects (knives, scissors, razor blades and even Sally's knitting needles). Making things worse is that a serial killer known as the Asylum Killer is on the loose and he has written a letter promising a double murder for his next crime. The couple make the best of it despite their fears and try to celebrate. However, after drinking drugged champagne they are knocked unconscious and awake to find their house covered with a fumigation tent and poison gas being pumped into their house. Now they must find a way to escape before they are overcome by the gas.
Numerous bits of evidence indicate McMillan's former girlfriend shot and killed her husband, but the commissioner wants all of the facts before an arrest is made.
