The Gorilla plot
"Out of the underworld comes the Gorilla---strangler of men---kidnapper of women! In come Mulligan and Garrity, two famous detectives who hear all, see all and know nothing! Out go the lights---on go the thrills! Shrieks! Yells! Roars! Screams! More Shrieks!"
Mystery surrounds a series of brutal murders of several individuals, including Cyrus Townsend, Alice's father, who was murdered in his home. It is speculated that the killer is a real gorilla. Detectives Garrity and Mulligan are sent to solve the case. They begin to search for the culprit, whom they are sure is one of the people present. It leads to suspicions from Arthur Marsden, his secretary and his partner Alice.