In the basement prison below Toronto’s largest market, two women named Mary—one a shunned, pregnant Irish immigrant, the other a vilified Mississauga woman—become an unlikely pair as they form a friendship within their cold, shared cell. Their bond threatens fellow inmate Sophia—who calls herself the first Black woman in Canada and the leader of the prisoners—and she plots to use the women to gain better treatment for herself. But as melting ice water pours into the prison from Lake Ontario, the forgotten women of Toronto must come together to survive.