Vinnie Miner, a small, plain and unmarried Ivy League professor, is on her way to London for a six-month study leave.
On the flight she is forced to share the company of Chuck Mumpson, a balky balding man in a tan western suit and rawhide tie, and as the plane touches down she hopes never to see him again.
Professor Vinnie Miner is happily established in London's literary society when her path crosses with young handsome colleague Fred Turner, also on a sabbatical, who has become involved with Rosemary Radley, an eccentric English actress.
By a chance meeting, Vinnie becomes re-acquainted with Chuck Mumpson and against her better instinct agrees to help him in a quest for his English ancestors.
Meanwhile Fred, estranged from his wife in America, believes he is in love with Rosemary.
Chuck arrives unannounced on Vinnie's doorstep for whisky and sympathy.
Fred, Vinnie and Chuck meet up at a drinks party given by Rosemary Radley.
To Vinnie's surprise Chuck is an instant success with the other guests, but the evening ends in disaster for Fred.
Whilst Fred and Rosemary are estranged, a late night visit brings Vinnie and Chuck closer together.
Vinnie and Fred are both suffering with pangs of guilt; Vinnie over her new relationship and Fred about Roo, the wife he has left behind in America.
Fred makes a shocking discovery when he tries for one last reconciliation with Rosemary Radley.
Prompted by thoughts of Chuck, Vinnie embarks upon an uncharacteristic mission of mercy.
Vinnie suspects that Chuck's affections have cooled, until a phone call turns her world upside down.