Wallace Fitch was the assistant of Mr Pemberton. Unknown to Wallace, Mr Pemberton was under the influence of the Rutans. He was taken to Chelsea 426 gardens and sprayed with Professor Wilberforce's perfume. This made him also fall under control of the Rutans. His task was to get to the Doctor, the archenemy of the Rutans. He gave tickets to the Carstairs family. The only member of the family who did not go to the garden event was the Carstairs' father. It was the Tenth Doctor who got to go. While the gifting of the tickets was part of a trap to infect any guests to the show with the Rutan virus, the only person who got infected was Bess Carstairs.
Wallace chased the Doctor and the twins into the TARDIS, where they were hiding with a man known as the Major. In a struggle, the Major was killed by the infected Wallace. When the Doctor returned to the TARDIS, he released excess oxygen into his ship, which freed Wallace from the Rutan Virus. The newly cured Wallace assisted the Doctor and the Carstairs twins in defeating the Sontarans and the Rutans, saving Chelsea 426. With the crisis averted and the Doctor heading off to a new adventure, a romance began to blossom between Wallace and Vienna Carstairs. (PROSE: The Taking of Chelsea 426)