Doctor Leon Perkins was a human physicist. He worked under Dr Irene Schulz.
He and Dr Schulz travelled in time using a prototype vortex manipulator, of their own creation. On their first test run, however, they were pulled off course, and materialised in the Hoarder's inner layer. The Hoarder decided that they were both his property, and took their future great-grandchildren as hostages. Schulz and Perkins were tasked with acquiring treasure for him, as well as hunting other children to further the Hoarder's grander extortion scheme. Together, they refused to acquire any living beings for him, and were summarily punished. Dr Schulz was also injected with a poison, the antidote for which was only provided on the successful completion of a mission.
Together they were tasked with procuring a painting from 1899. By mistake they travelled to 1999 and took the painting from a small museum, bringing it back to their client in exchange for a shot for Dr Schulz. (COMIC: A New Beginning)
At some point, Perkins' vortex manipulator was sabotaged, and he was caught in a time loop. The portal he was trapped in appeared at various points through time and space, with his hand sticking out and repeatedly uttering the words "grab on! I can't...can't hold...", and also briefly appeared in front of the Doctor at different points in their lives. He appeared aboard the SS Madame de Pompadour in front of the Tenth Doctor, who failed to reach his hand before vanishing, in Amy Pond and Rory Williams's back garden during the Year of the Slow Invasion, without being noticed by the Eleventh Doctor, and inside the lift of the Mondasian colony ship in front of the Twelfth Doctor, Nardole, and Missy. (COMIC: A New Beginning, The Road to...)
Finally, in 3912, the Thirteenth Doctor, Yasmin Khan, Graham O'Brien and Ryan Sinclair saw the portal on Blecplam Two and a Half. The Doctor calculated the space-time coordinates he would pop out next, and there Ryan and Yasmin pulled him out. Perkins was then taken prisoner by the Grand Army of the Just, along with the Doctor and her friends. Once they had escaped, Perkins drew out a gun, briefly attempted to take over the Doctor's TARDIS, though he was soon talked down.
Later, having located and reunited with Schulz, Perkins returned with her to the Hoarder's lair, with the Doctor and company close behind with the TARDIS. After announcing that they would no longer work under these conditions for the Hoarder, Perkins threw his vortex manipulator in the Hoarder's direction. As planned, the Hoarder attempted to use the device, and became trapped in the same time loop Perkins himself had recently inhabited. (COMIC: A New Beginning)
He and Schulz later joined the Time Agency, (COMIC: Hidden Human History) on account of the Doctor's recommendation to the Agency. (COMIC: A New Beginning)
