No, it's not the only wire in the circuit. If that plug is plugged into an outlet, then the hot live wire is coming into the circuit at the pin labelled live, and connecting to the ground wire of the device. That ground wire is usually connected to the metal frame of an appliance. Because of the white wire connecting the live and neutral pins together, it's going to immediately flow back to the breaker box. However, if for whatever reason the path from the ground of the device to actual ground is shorter, then the electricity will flow through the device. It is possible for a person to be in the path to ground. The way this is wired might also circumnavigate an RCD, preventing the safety switch from operating correctly.