This is not, in my opinion, one of the great noirs, but it tells a fast-paced, well-acted story with style, tension and humor. Ray Milland plays George Stroud, dynamic editor of a crime magazine, one of many in Earl Janoth's (Charles Laughton) publishing empire. Through circumstances, he meets Laughton's mistress one evening. She later is killed. Janoth puts Stroud in charge of tracking down the murder to get an exclusive for the magazine...(not much of a spoiler ahead; the killing is shown early)...and to cover the fact that Janoth was the killer. Milland is quickly set up to take the fall.
Milland was edging into middle age and this added to the authority he brought to the role. Although he still had the charm and light comedy springingness, he is believable as a quick-thinking potential victim.
Laughton is first rate. In a couple of scenes he scurries to the elevator or across a hall and looks like a fat, dangerous spider. He helps define Janoth's character as an indulgent, morally corrupt egoist by touching his mouth and grooming a small, ridiculous moustache with a little finger.
Rita Johnson plays the mistress and is terrific. She's shrewd, sexy and sophisticated. She didn't have much of a career and, according to IMDb, apparently had a death worthy of a noir movie.
George Macready plays a smart, cold, condescending lawyer whose ethics are flexible. His range may have been be limited, but Macready was one of Hollywood's great character actors.
You might be able to find an old, used paperback of the book by Kenneth Fearing. He was a good poet who never made it. In the three or four mystery/novels he wrote he uses the device of having the characters speak for themselves in the first person, each to his or her own chapter. It takes getting used to but it becomes quite effective. Dagger of the Mind and The Loneliest Girl in the World also are very good and also, I suppose, long out of print. If you like mysteries (or dead American poets), give him a Google.
Kevin Costner's No Way Out was based on the book and this movie. In the ring, I'd give Milland over Costner on points by a wide margin; Laughton over Hackman on points but close; Macready over Patton by a knockout in the sixth; and Johnson over Sean Young by a knockout in the first. And this version over the other by a knockout in the fifth. No Way Out's conclusion is, for me, unsatisfying because it drains sympathy from the Costner hero. In The Big Clock, the ending is satisfyingly concluded with an elevator shaft and, later, a hug and a laugh.
The DVD transfer is quite good considering the age of the movie, and shouldn't be a reason for not getting the movie.