In The Third Wheel, love is in the air – but what does that mean for Greg Heffley? A Valentine's Day dance at Greg's middle school has turned his world upside down. As Greg scrambles to find a date, he's worried he'll be left out in the cold on the big night. His best friend, Rowley, doesn't have any prospects either, but that's a small consolation. Then an unexpected twist gives Greg a partner for the dance and leaves Rowley the odd man out. But a lot can happen in one night, and in the end, you never know who's going to be lucky in love.