Dirección: Charles Lamont
Abbott y Costello son dos detectives que reciben en su despacho a su primer cliente: un boxeador llamado Tommy Nelson acusado injustamente de haber matado a su mánager; un crimen que Tommy dice no haber cometido. Acompañado de los dos detectives, el púgil visita a un doctor, que le inyecta el suero de la invisibilidad, para que así pueda demostrar su inocencia
Bud Abbott
Bud Alexander
Lou Costello
Lou Francis
Nancy Guild
Helen Gray
Arthur Franz
Tommy Nelson
Adele Jergens
Boots Marsden
Sheldon Leonard
Boots Morgan
William Frawley
Det. Roberts
Gavin Muir
Dr. Philip Gray
Sam Balter
Radio Announcer
John Daheim
Rocky Hanlon
Walter F. Appler
Professor Dugan (uncredited)
Bobby Barber
Sneaky (uncredited)
Howard Banks
Officer (uncredited)
Richard Bartell
Bald Man (uncredited)
Phil Bloom
Fight Spectator (uncredited)
John Breen
Trainer (uncredited)
Milt Bronson
Ring Announcer (uncredited)
Ralph Brooks
Man at Bar (uncredited)
Steve Carruthers
Reporter (uncredited)
Tom Coleman
Dugan Detective School Graduate (uncredited)
