Michael Portillo, once a British cabinet minister who voted to keep capital punishment on the books, sets out to find whether any method of state execution can be called humane. He examines the electric chair, the gas chamber, and hanging, weighing eyewitness accounts and technical failures against each method's claim to painlessness, and pushes himself into direct physical tests of what condemned prisoners actually experience. The film's hinge is lethal injection, the method most US states now use, arriving as the Supreme Court is hearing arguments about whether it causes prisoners to die in unnecessary pain. Portillo talks to doctors, executioners, and researchers who have studied botched executions, building toward his own proposal for a different method he argues would be less cruel than anything currently practiced. The film treats execution as an engineering and medical problem as much as a moral one, and Portillo's willingness to test procedures on his own body gives the argument a bluntness that pure interview footage would not.