He is well known for his evil laughter followed the introduction from The Shadow radio drama: "Who knows what evil lurks in the hearts of men? The Shadow knows!". Readick replaced James La Curto to perform The Shadow narrator in the Detective Story Hour (the precursor of The Shadow) in 1930, four months after the launch of the series when La Curto went for a Broadway role. This signature line remained intact in The Shadow even after Orson Welles succeeded Readick.
He later played the doomed CBS reporter Carl Phillips in the 1938 radio production of The War of the Worlds. Readick modeled his performance on WLS reporter Herbert Morrison's coverage of the Hindenburg disaster the previous year.
He was also known for House of Mystery (1931) and A Burglar to the Rescue (1931).
He died in 1965 in the USA.