Doctor Irene Schulz was a human physicist, described by Dr Leon Perkins as the "foremost expert" on temporal physics.
She and Dr Perkins 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. Though they brought back many valuable objects, both refused to acquire any living beings for the Hoarder. They were summarily punished.
In addition to his other tactics, the Hoarder injected Schulz with a poison, and offered up a dose of the antidote on the completion of each of his tasks. 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 of the antidote.
At one point, she decided that she would seek freedom by endeavouring to make her own antidote. She intentionally sabotaged Perkins' vortex manipulator, in her best effort to keep him out of reach, and thus safe from the Hoarder, as she prepared. As a result, Perkins became trapped in a time loop, but he was pulled out by the Thirteenth Doctor and friends, who eventually reunited him with Schulz.
Following the Doctor's new plan, Schulz and Perkins returned to the Hoarder's lair, with the Doctor and company close behind with the TARDIS. The two announced that they would no longer work under these conditions for the Hoarder. To Schulz's surprise, Perkins threw his vortex manipulator in the Hoarder's direction. When the Hoarder attempted to use the device, he became trapped in the same time loop Perkins himself had recently inhabited, as planned. (COMIC: A New Beginning)
She and Perkins later joined the Time Agency, (COMIC: Hidden Human History) on account of the Doctor's recommendation to the Agency. (COMIC: A New Beginning)
