Boris Karloff
— Gruesome
Ralph Byrd
— Dick Tracy
Anne Gwynne
— Tess Trueheart
Edward Ashley
— Dr. L.E. Thal
June Clayworth
— Dr. I.M. "Irma" Learned
Lyle Latell
— Pat Patton
Tony Barrett
— Melody
Skelton Knaggs
— X-Ray
James Nolan
— Dan Sterne
Joseph Crehan
— Chief Brandon
Milton Parsons
— Dr. A. Tomic
Ernie Adams
— Waiter at Hangman's Knot (uncredited)
Phil Arnold
— Sneezing Bank Customer (uncredited)
Walter Bacon
— Bar Patron (uncredited)
Lex Barker
— City Hospital Driver (uncredited)
Eddie Borden
— Bank Customer (uncredited)
Robert Bray
— Sergeant (uncredited)
Robert Clarke
— Fred (Police Analyst) (uncredited)
George Cooper
— Stone (Bank Teller) (uncredited)
Suzi Crandall
— Blonde Bank Customer (uncredited)
William Gould
— Pop (uncredited)
Ben Hall
— Luke (Police Stooge) (uncredited)
Harry Harvey
— Humphrey (Bank Guard) (uncredited)
Tom Keene
— Dr. Frankey (uncredited)
George Lloyd
— Owner of the Hangman's Knot (uncredited)
Robert Malcolm
— Doctor (uncredited)
Sean McClory
— Officer Carney (uncredited)
Lew Meehan
— Police Driver in Montage (uncredited)
Bruce Mitchell
— Police Sgt. in Montage (uncredited)
Lee Phelps
— Detective (uncredited)