The film was thought to have been lost until it was rediscovered in the 1970s. A newly restored 35mm print has been made, and the restored version was first shown at the 2011 H.P. Lovecraft Film Festival.
In 1784, shortly after the United States wins its independence, American Peter Standish (Leslie Howard) sails from New York to England to marry his cousin. Upon hearing of a Frenchman crossing the English Channel in a balloon, Peter regrets that he will not be able to see the marvels the future has in store.
In 1933, his descendant, also named Peter Standish (Leslie Howard again), unexpectedly inherits a house in Berkeley Square, London. He becomes increasingly obsessed with his ancestor's diary, causing his fiancée Marjorie Frant (Betty Lawford) great concern. When they have tea with the American ambassador (Samuel S. Hinds), Peter confides to the diplomat with eager anticipation his conviction that he will be transported back 149 years at 5:30 that day. Peter is convinced that all he needs to do is follow his ancestor's diary, since he already knows what happens, from reading it.
He rushes home, and just as he opens the door, he is indeed back in 1784, taking the place of the earlier Peter Standish just as he arrives at the house, then owned by his relations, the Pettigrews. Lady Ann (Irene Browne), and her grown offspring, Tom (Colin Keith-Johnston), Kate (Valerie Taylor) and Helen (Heather Angel) are there to greet him. The Pettigrews, being in desperate financial straits, are anxious for Kate to marry the wealthy American. Peter is determined not to alter the future he has read about, until he sees Helen for the first time. He tries to fight his attraction to her, but ultimately fails. Helen, meanwhile, is being pressed by her mother to marry Mr. Throstle (Ferdinand Gottschalk), but, Helen has determined, even before Peter's arrival, not to marry. She later confesses to Peter, that she had been dreaming of him, before she saw him.
As time goes on, Peter keeps inadvertently giving offense with his unfamiliarity with 18th century customs. People also begin to fear him, as he blunders and speaks of things which have not yet taken place. For example, when he commissions Sir Joshua Reynolds to paint his portrait, he praises another Reynolds work by name, one the painter has only just begun. Kate becomes convinced that Peter is demonically possessed and breaks their engagement. Helen, however, is sympathetic to his difficulties, and falls in love with him.
Helen eventually presses Peter for an explanation of his "second sight", which he has only hinted at. Though he refuses to speak openly, she somehow sees in his eyes visions of his modern world, with all its horrors as well as its marvels, and guesses the truth. Knowing he has become disillusioned, living among ghosts born 149 years before his time, and desperately unhappy with the day-to-day realities of her era (including a lack of hygiene and plumbing, and not bathing regularly in what he calls a "filthy little pigsty of a world"), she urges him to return to his own time. He wants to stay with her regardless of the consequences, but in the end, he does go back to 1933.
When he visits Helen's grave, he learns that she died on June 15, 1787 at the age of 23. Marjorie comes to see him, worried about his sanity because he has been saying that he is from the 18th century. Peter believes his ancestor had switched places with him. He tells her he cannot marry her. Peter is consoled by the epitaph on Helen's grave, and her conviction that they will be together, "not in my time, nor in yours, but in God's".
The film was a box office disappointment for Fox.
The New York Times reviewer Mordaunt Hall called it "an example of delicacy and restraint, a picture filled with gentle humor and appealing pathos." He particularly praised Leslie Howard, writing, "He has done excellent work in other films, but it is doubtful whether he has ever given so impressive and imaginative a performance." Variety declared the film "an imaginative, beautiful and well-handled production," but predicted that it would not fare well at the American box office because of the very British cast and dialogue. John Mosher of The New Yorker also praised the film, writing that "the charm that was in the play is there, with Leslie Howard again in his stage role, and with the good, even poetic, lines conserved, and the handsome eighteenth-century London mounted for us with a great deal of taste." Harrison's Reports wrote: "Artistically and handsomely produced and beautifully acted, "Berkeley Square" emerges as high-class entertainment for the better class of picture-goers; it is rather slow for the masses."
The film was remade in 1951 as The House in the Square, starring Tyrone Power and Ann Blyth, but shown in the U.S. as I'll Never Forget You. Irene Browne reprised her role as Lady Ann Pettigrew in the remake.