When gangster Tommy Ramsey is released from prison, he is determined to retake control of his East End territory. But new arrivals threaten his grip on illegal activity in the area. An evangelical minister is persuading people to seek redemption for their sins. A new gang is claiming the streets. And a watchmender called Smith is leading a revolt against the Ramsey Mob's protection racket. When Tommy strikes back at his enemies, a far more terrifying threat is revealed. Within hours the city's air turns into nerve gas and thousands succumb to the choking fumes. London is dying. An adventure set in 1950s London, featuring the Third Doctor as played by Jon Pertwee and his companion Sarah Jane Smith.