Alvin suspects that Dave is leading some kind of double life. After Alvin spies on Dave, he thinks Dave's being blackmailed and hiding a secret, especially since a man in a trenchcoat and viola case is seen following Dave. Alvin, Simon, and Theodore each interview some of Dave’s old friends to find out what his secret might be. They spilt up and each see one person; a sushi chef skilled with a ginzu knife who remembers that a young Dave bashed his bicycle, a tough lumberjack who got a black eye when he and Dave fought as kids, and a woman who has buried many husbands who is annoyed that Dave dumped her. They surmise the three must be plotting their revenge, and the strange man in the trench coat is a hired gun. At the concert, they put themselves in the orchestra to "save" Dave. They soon learn that Dave has a violin and piano show with his old music teacher, who was the strange man with the viola case, and that the three people they interviewed are in the front row of the concert, not out of spite but to see his performance. To show how sorry they are, the Chipmunks sing "I'm Sorry", then Dave performs his concert as scheduled.
- "I'm Sorry" originally performed by Brenda Lee.