The character first appears in The Red Lady, where she met the Eighth Doctor and Liv Chenka who were in search of a temporal anomaly related to the Eleven while working as an assistant to Professor Walter Pritchard. She joined them in their investigation of artifacts connected to the Red Lady and helped them defeat her. Helen was dismissed from her position, as her boss was suspicious that she was behind the artifacts' theft, and accepted the Doctor's offers to join him and Liv on their travels. She joins their efforts to track down the dangerous Time Lord criminal the Eleven. During her travels with the Doctor, she encounters River Song, with River trusting Helen with the secret of her true history with the Doctor despite the risk of a younger Doctor learning about her existence. One trip sees Helen meet her brother in 2008, during which she learns that she can never return to her time despite her family's reputation being seriously tainted by her apparent theft of the artefacts, forcing her to claim to be her own daughter. In the final episode of Doom Coalition, Helen is last seen trapped in a damaged TARDIS with the Eleven. She returns in the following audio series, Ravenous, where she has spent some time trying to help the Eleven after the TARDIS crash-landed in an asylum, but her efforts are proven to be a failure as the Eleven attempts to take control of the local system with the aid of the Kandyman. Having rejoined the TARDIS crew, Helen gets caught up in a crisis in Salzburg when a mysterious wish-granting entity causes the Krampus to become real. To stop this threat, Helen spends thirty years piloting the TARDIS until she finds Bishop Nicholas in the fifth century, the original inspiration of Father Christmas, bringing him into the present so that he can order the Krampus to release its victims, Liv using her own wish to restore Helen to youth. As the TARDIS crew are forced to join the Eleven to face the Ravenous, a race of beings who essentially 'eat' regeneration energy, Helen is briefly abducted by Missy- a female incarnation of the Master- to translate a map that leads to the location of Artron, an ancient Time Lord scientist. Artron is revealed to be the wish-granter the trio encountered in Salzburg, who unintentionally created the Ravenous when he was manipulated by the Master into draining the energy from a mysterious race. As the Eleven joins the Ravenous to try and destroy the universe, the two aforementioned Masters join forces with the War Master to confront the Eleven, while the Doctor is able to help Artron realise how he can undo his mistake and 'cure' the Ravenous, restoring them to their original state at the cost of his own life.
