Sorin

Captain Sorin was the leader of a Red Army commando unit who arrived at Maiden's Point by way of Northumberland, in 1943. His mission was to steal the ULTIMA machine. Unbeknownst to him, Commander Millington had leaked the information about its location so that when the Soviets stole it and used it to decode British cyphers, a deadly poison would be released.

Sorin took a liking to Ace and gave her his scarf. Admiring her bravery and skill, he subsequently gave her his cap insignia when she noted that the Soviet patch on her jacket was merely a cheap reproduction. (TV: The Curse of Fenric) That insignia later served as a catalyst for Ace's taming of the Cheetah Woman Karra. (TV: Survival)

Sorin was killed when Fenric took possession of his body. (TV: The Curse of Fenric)

Sorin's death would haunt Ace throughout her remaining travels with the Doctor. (TV: The Curse of Fenric) She named her cat after him, (PROSE: At Childhood's End) and also noted that Sorin greatly resembled his great-grandfather Nikolai. (PROSE: The Curse of Fenric)