The key to a flat in wartime Britain may augur bad luck for a succession of tug captains of the Royal Navy whose task is to rescue crippled ships in "U-boat Alley." As each takes possession from his unfortunate predecessor, the flat's other occupant, a Swiss expatriate named Stella, apparently goes with it. The latest captain struggles with his conflicting fears and affection for its apparent jinx.
American David Ross (William Holden), a former tugboat captain now in the Canadian army, is hastily commissioned in the Royal Navy and assigned to rotating command of W88, a double-screwed rescue tug then in dry dock due to battle damage. His predecessor was a suicide. The slow, poorly armed tugs bring in "lame ducks," freighters crippled near Britain by German attacks. The main danger is from U-boats and aircraft.
David is reunited with an old friend, Captain Chris Ford (Trevor Howard), who commands another tug about to go on a mission. Chris takes David with him and they are attacked twice. That night Chris brings him home to his flat to meet his lover, Stella (Sophia Loren), who wears a wedding ring. She had been engaged to Philip Westerby, another tugboat captain, but he was killed the day before their wedding. A friend of Chris's, Van Barger, took possession of the hard-to-find flat and Stella stayed with him. Knowing the extreme danger of his job, Van Barger then gave a copy of his key to the flat to Chris, so that Stella would be taken care of no matter what. When Chris chooses David to be the next in line, he tries to refuse, but his friend is insistent.
David's tug comes out of dry dock and he goes aboard to take his turn of command from the tug's other captain, Van Dam (Oskar Homolka), who gives him tips for survival in combat but warns him that his real enemy is the one within himself, fear. Shaken by his recent close call, Chris proposes marriage to Stella, who accepts. However, she has a premonition that he will not be coming back from his next mission. She is proved correct.
At first, David refuses to move in. When he eventually does, he is surprised that Stella does not share his bed, but as time goes by, she falls in love with him, unlike the others. She puts away her photograph of Philip, gets rid of the uniforms of David's predecessors, and takes off the wedding ring. She also leaves her flat for the first time since Philip was killed. Finally, she asks David to marry her, and he gladly accepts.
With the U.S. entry into the war, an American freighter becomes David's next assignment, even though it is Van Dam's turn. Its inexperienced crew sends out a continuous S.O.S., contrary to sealed orders, revealing the ship's position to the enemy. When David finds out the situation, he tries unsuccessfully to refuse what amounts to a suicide mission. Knowing his chances, he gives his key to the new captain of another tugboat, Chris's former mate, Kane (Kieron Moore).
David's tug is attacked by a U-boat and hit numerous times. He orders the crew to abandon ship, then rams the submarine. After being rescued, David hurries back to the flat, but Kane is already there, having told Stella that David was killed. When she sees him alive, she screams at him to get out, hurt to the core by his betrayal in passing on the key. Later, Kane finds David drinking his sorrows away, and informs him that Stella is leaving for London on the train. David does not arrive at the station in time to board the train, but vows to Kane that somehow he will find her.William Holden as David Ross
Sophia Loren as Stella
Trevor Howard as Chris Ford
Oskar Homolka as Captain Van Dam, who alternates command of the tug with David
Kieron Moore as Kane
Bernard Lee as Wadlow, the head of the salvage unit
Beatrix Lehmann as Housekeeper
Noel Purcell as Hotel Porter
Bryan Forbes as Weaver, Mate of W88
Sidney Vivian as Grogan
Rupert Davies as Baker
Russell Waters as Sparks
Irene Handl as Clerk
John Crawford as American Captain
Jameson Clark as English Captain
Two endings for The Key were filmed. According to "Notes" at the Turner Classic Movies entry for the film and attributed to the New York Times, one was filmed in which David gets aboard the train for a "happy" ending. In the other, purportedly filmed to satisfy the American Motion Picture Production Code by showing that David and Stella pay for their sexual relationship, he just misses catching it, but insists he will search for and find her. In this explanation the Production Code Administration unexpectedly accepted the happy ending but a few reels of the darker ending were distributed to meet the demands of cinemas during its opening run.
However a published history of British films subjected to PCA scrutiny before their American release presents a slightly different version. After an initial rejection of the story outline in 1952 by the PCA, Carl Foreman resurrected the Stella project in 1957 and was offered two acceptable story lines: one in which Stella has an unconventional but asexual relationship with the captains, the other "a clearcut story of sin and retribution" in which she loses her relationship at the end. The source states that the second version was submitted to the PCA and a certificate issued in June 1958.
A biography of director Carol Reed by Peter William Evans supports the latter contention. It asserts that the original ending released in Europe had David missing the train, and that Reed intended to convey that his vow to find Stella has no more substance than "the steam in which both they and the moving train are shrouded." Evans adds that the happy ending of David catching the train was made for U.S. audiences and was a more "conventional conclusion."
De Hartog's novel, originally entitled Stella, concerned Dutch tugboat captains who fled to England with their craft in 1940 (as represented by the character Captain Van Dam and based on historical fact) and a British woman named Stella. The casting of Holden and Loren necessitated script rationales for their presence in 1941 England, but the appointment of an American in the RNVR as a ship's captain during the early years of World War II was historically possible.
Filming of The Key was done aboard H.M.S. Restive (W39), an Assurance class Admiralty tug of the Royal Navy from the same era.
Trevor Howard won the BAFTA Best British Actor Award in 1958 for his performance.