Nuclear physicist Christopher Thorn was a colleague of Sir James Braddock, secretly an agent of Merlyn. Sir James constructed a sentient computer, Mastermind, in Braddock Manor, but it slew Sir James and his wife, then took over Thorn's mind, granting him powers and transforming him into its agent, Doctor Synne. He terrorised and enslaved people living near the manor, before finally targetting Sir James' eldest son, Jamie Braddock, who had returned home to Braddock Manor and was now the only family member in residence. Synne's attack brought Jamie's siblings, the twins Betsy and Brian, back home, but Synne attacked them en route, until Brian transformed into his alter ego, the super hero Captain Britain, and drove him off. Synne made another attempt on the Braddocks soon after the twins reached the manor, taking control over Betsy's mind from a distance and forcing her to attack her brothers. After Brian subdued her, Synne provoked another confrontation with Captain Britain by manipulating local villagers into attempting to burn a woman at the stake; when Captain Britain intervened, Synne attacked him. The Mastermind computer, remotely powering Synne, channeled extra energy into its pawn, allowing him to gain the upper hand, but before he could slay the hero, Braddock Manor's housekeeper, Emma Collins, unplugged the computer while cleaning, unwittingly cutting Synne off at the crucial moment and he reverted to being Christopher Thorn. The shock of suddenly being freed from Mastermind's control proved too much for Thorn's body, and he died after warning Captain Britain of the need to stop Mastermind.