Kotch, played by Walter Matthau, is a grandfather who shares a home with his son Gerald (Charles Aidman), his wife Wilma (Felicia Farr), and their young child Duncan (Donald Kowalski). Duncan’s behavior often causes Kotch difficulty. His daughter-in-law hires Erica (Deborah Winters) to help care for the children, which Kotch doesn't appreciate. While trying to secretly find out what’s going on, he discovers that she and her boyfriend aren’t being careful, but figuring out how to tell Gerald without revealing his own snooping proves tricky. Wilma is fed up with her father-in-law, so Gerald reluctantly agrees it’s time for Kotch to move into a separate room with dated decor. However, Kotch isn't easily fooled and manages to trick a psychologist, leading him to decide on taking a trip of his own. During this journey, he unexpectedly runs into Erica again; she is now pregnant and struggling financially. He decides to rent a house and offers her a job as his housekeeper, setting the stage for them to live together and experience various adventures as they await the arrival of baby Chris. There was always something special on screen when Matthau worked with Jack Lemmon, and although Lemmon is behind the camera this time, Matthau truly embodies the role of the clever older man; the film moves along pleasantly, though not entirely believably, for nearly two hours. The length is likely its biggest drawback because while there are certainly some funny and touching moments, it lacks sufficient development to carry the story. Matthau’s chemistry with Winters works well, but otherwise much of what's presented feels forced and a little awkward to witness. I found the ending appropriate, if somewhat melancholy, but ultimately felt just a bit let down by the entire experience.

Source on TMDB