"The Accidental Husband" centers on Emma (Uma Thurman) a successful but uptight relationship expert with a hit radio show and an upcoming book. She is serious and sensible about the issue of love and gives frank, 'on the nose' advice to women on how to find the right man without wasting time on the wrong ones in between. Emma believes she has met her own perfect match in Richard (Colin Firth) a successful and conservative publishing executive.
Of course matters of the heart are never as clean cut as Emma believes them to be! Just weeks before her wedding Emma discovers she is somehow already married to Patrick (Jeffrey Dean Morgan) an irresponsible but charming neighborhood fireman with a big secret ...the marriage is no accident.
It turns out Patrick is harboring a grudge -- his fiancee broke up with him after receiving relationship advice from Emma on her show. The "accidental" marriage is a prank Patrick pulled to cause chaos in Emma's apparently perfect love life and show her what it feels like to have a complete stranger meddle with your life.
Unable to come clean, Patrick goes along with the ruse pretending to be just as baffled as Emma. Whilst trying to figure out how to end the marriage their opposite approaches to life create much tension and chaos. But as they spend more time together, Patrick starts to fall in love with the woman he thinks ruined his future marriage and Emma starts to admire his carefree, reckless passion for life and doubt her own conservative, button-down views on life and love.