Toby worked at Sanctuary Base 6 when Rose Tyler and the Tenth Doctor arrived and were subsequently stranded. He copied down fragments of the script that were on pieces of ancient pottery, but was unable to translate it.
He explained to the Doctor and Rose the Walker Expedition was looking for an "unnatural" power source at the centre of the planet, releasing a gravity field that kept the planet in orbit. He knew that the extinct civilisation that existed before on the planet had buried something and "Now it's reaching out. Calling us in." As the Expedition's excavations reached their late stages, Toby kept hearing the voice of the Beast, which eventually possessed him. While possessed, Toby ventured outside onto the planet's surface.
Later, Scooti Manista, another member of the crew, heard him leave when she was dropping off some paperwork. She found him outside the base, surviving in deep vacuum without a spacesuit. Toby grinned and gestured to her. She raised her arm towards him, hypnotised. However, she eventually broke his hold on her and yelled at him to stop. Angered, Zed began to break the window. Scooti tried to escape, but Toby had sealed the doors, trapping her. Soon the window shattered and Scooti was dragged out into space screaming.
Toby quickly joined the others to avoid the hull breach. Toby told no one that he killed Scooti. After Ida and the Doctor went down, he was repossessed along with the Ood. They began killing off the crew. (TV: The Impossible Planet)
Though Toby was "freed", the Beast remained free to possess him if it wished. Toby followed Danny Bartock, Mr Jefferson and Rose through the maintenance tunnels so Danny could release a "flare" that disrupted the Ood's telepathic field; Mr Jefferson sacrificed his life to buy time for the others. As the Sanctuary Base 6 rocket left the planet with Rose on board, the Beast manifested itself in him. Rose unbuckled his seatbelt and used a bolt gun to smash the window. An emergency window prevented the ship from de-pressurising and Toby flew through space, into the black hole and to his death, taking the Beast with him. After his death he was awarded posthumous honours by Captain Zachary Cross Flane. (TV: The Satan Pit)
Toby Zed had a quiet manner, though Rose also upbraided him for his dramatic nature, calling him "Chief Dramatist". (TV: The Impossible Planet) While attempting to use the personal fears and weaknesses of the Doctor, the crew and Rose against them, the Beast revealed to the others that Toby, already into his twenties, was a virgin. (TV: The Satan Pit)
Special abilities and features whilst possessed edit
While the Beast took him over, Toby's irises turned red and the script appeared on his body. He displayed a form of telekinesis, survived vacuum unscathed, spoke with the voice of the Beast (TV: The Impossible Planet) and could issue flame from his mouth. (TV: The Satan Pit)