Introverted and steady Joel Barris (Jim Carrey) met the straightforward and casual Clementine Kroskey (Kate Winslet) at a party, and the two became lovers. Like ordinary lovers, their days were spent in sweetness and quarrels. On the eve of Valentine's Day in 2004, when Joel carefully prepared a gift and went to Clementine to apologize for a quarrel not long ago, he was surprised to find that Clementine didn't remember him at all. It turned out that the impulsive Clementine couldn't stand the pain of quarrels in their relationship, so she went to the "Forget Love Clinic" and deleted all her memories of Joel. Joel couldn't forgive Clementine's willfulness, nor could he bear the pain of losing her, so he also went to the "Forget Love Clinic" and asked Dr. Howard (Tom Wilkinson) to erase his memory of Clementine. The memory clearing program started, and Joel wandered in his memory. He found that the time he spent with Klestin, whether it was painful or sweet, was precious, and he didn't want to forget the woman he loved deeply. However, once the program is started, it cannot be reversed. Joel can only try his best to hide Christine in the deepest part of his memory, in those corners of time where Christine has never appeared in reality, in order to preserve this love...