After graduating from"Dugan's Detective School"..inept private investigators:Bud"Alexander"(Bud Abbott) and Lou"Francis"(Lou Costello)agree to help prove that former boxer"Tommy Nelson"(Arthur Franz)..who becomes invisible with the aide of a serum created by his girlfriend's uncle"Dr.Phil Grey(Gavin Muir)that he was framed for murdering his manager by crooked sports mobster"Morgan"(Sheldon Leonard).