Hal Korwin was the husband of Kath McDonnell. He was one of the crew of the SS Pentallian.

Hal was possessed by the star Torajii and started killing the crew. He wore a welding helmet to keep his eyes from shining all the time. He also transferred his powers to Dev Ashton.

Even when possessed, Korwin recognised his wife, but claimed, "It's all her fault". Hal was temporarily stopped when the contents of a coolant vent were poured on him. However, the bit of Torajii left in him got strong enough to repossess him as the ship got closer to the main star. Regaining consciousness, he disabled the med centre power, where the Doctor was trying to freeze Torajii out of him before being completely possessed by it. Kath had tried to reactivate the power, but was forced to lure him to an airlock and eject both of them into space to save the others. They flew into space in each other's arms. (TV: 42)