After years of severed communication, Justin appears on his sister's doorstep needing a place to stay. The home he's made for himself has collapsed, as has everything else in his life. When they were children, Willa played the role of her brother's protector, but now, afraid of the chaos he might bring, she's reluctant to let him in.

Willa lives a carefully ordered life working as a nurse and making ornate dioramas in her spare time. As Justin tries to connect with the people she's closest to--her landlord, her boyfriend, their mother--she begins to feel exposed. Willa and Justin's relationship has always been strained yet loving, frustrating and close. But it hits a new breaking point when Justin spirals out of control, unable to manage his sobriety and the sustained effects of a brain injury.

Years earlier, in high school, desperate to escape his home life and his disapproving, troubled mother, Justin falls into the hands of his first lover, a slightly older boy living on his own who offers Justin some semblance of intimacy and refuge. When Justin's boyfriend commits a terrifying act of violence, the two flee on a doomed road trip, a journey that will damage Justin and change his and his family's lives forever.

Weaving together these two timelines, Brother & Sister Enter the Forest unravels the thread of a young man's trauma and the love waiting for him on the other side.