Night Man by Allan Ullman
(from the screenplay by Lucille Fletcher)
First published 1951; cover shown is the 1958 Corgi Books (UK) paperback edition. Cover art by Oliver Brabbins. 156p.
"As she stepped into the lift, she realised that it was not the usual attendant. For an instant, terror clamped its fingers about her heart. His eyes met hers briefly - and a shock of recognition stabbed her. But it couldn't be... It couldn't be the only man in the world she feared... or could it?"