Sarah Polley is best known as an actor, but she decided to make this film about her family, specifically her vivacious mother and the affair she had with Polley’s father. This film is made up of interviews with every member of her family (and then some), as well as lots of footage from their past. The momentum until she discovers the truth is well-paced and compelling. The last third bogs down in wordy debates about truth and memory (fewer people translates into less energy). There are surprises which upend the entire project, but you’ll have to sit thru it to find out. If ur into talky docs, you might find it worthwhile.