Mark Hogancamp suffers brutal injuries after a vicious attack by a group of neo-Nazis, leaving him with almost no memory of his previous life. In the wake of this trauma, Mark struggles to piece his world back together and faces the daunting task of reconstructing his identity. Suffering from PTSD, he discovers a unique and creative form of therapy to help him cope with his psychological wounds. Instead of turning to conventional treatment, Hogancamp constructs an elaborate 1/6 scale World War II-era Belgian town in his backyard, which he names Marwen.

Marwen becomes a therapeutic landscape, populated by dolls representing his friends, his attackers, and himself – a fictional character named Captain Hogie, who is the town's hero. As Hogie, he stages intricate and fantastical photographic stories that mirror his own fight against his oppressors and his journey of healing. However, as his court date to confront his attackers approaches, the lines between reality and fantasy begin to blur. Mark must navigate his complex emotions and determine if he can truly overcome the trauma of his past and the fears that haunt him.