When the wedding of internationally famous film star Lara Tyler (Alice Eve) to tweedy English author James Arber (David Tennant) is sabotaged by the paparazzi, they decide to relocate the event to the one place where the world's press won't find them: the sleepy island of Hegg. But, one ingenious press photographer has tracked them down in his mission to capture the celebrity wedding of the year. Now, Lara's assistants must find a decoy bride to distract the media, and they think that local girl Katie (Kelly MacDonald) will be the ideal replacement. But when Katie meets James, sparks fly, dresses get ruined and love gets complicated. Will Katie be able to fool the press pack, and make a convincing stand-in for the world's most famous movie star? And whatever will happen to her pledge to never, under any circumstances, fall in love again?