Wiener-Dog tells several stories featuring people who find their life inspired or changed by one particular dachshund, who seems to be spreading a certain kind of comfort and joy. Man’s best friend starts out teaching a young boy some contorted life lessons before being taken in by a compassionate vet tech named Dawn Wiener. Dawn reunites with someone from her past and sets off on a road trip picking up some depressed mariachis along the way. Wiener-Dog then encounters a floundering film professor, as well as an embittered elderly woman and her needy granddaughter—all longing for something more.
After the death of his older brother Joe, Lee Chandler (Casey Affleck) is shocked that Joe has made him sole guardian of his teenage nephew Patrick. Taking leave of his job as a janitor in Boston, Lee reluctantly returns to Manchester-by-the-Sea, the fishing village where his working-class family has lived for generations. There, he is forced to deal with a past that separated him from his wife, Randi (Michelle Williams), and the community where he was born and raised.