Kate Sherrin worked at Ambermouth Seacology Centre alongside Jim.
In 2013, Sherrin and Jim began collecting the bodies of birds that had fallen victim to the quartz that was growing in Ambermouth harbour — a by-product of Eldrad's presence. A beluga whale, infected by the crystal, was taken in by Sherrin and Jim, despite not having the appropriate facilities to house it. They named it Skipper and kept it in the centre where it was dosed with morphine.
While near the shore, she saw the Fifth Doctor, Tegan Jovanka, Turlough and Nyssa. Sherrin approached them to ask them to leave — the shoreline being a restricted area, due to the deaths and radiation. She gave Tegan medical assistance after she cut her leg paddling.
Sherrin took another gannet that Turlough and Nyssa found dead and covered in quartz back to the centre, asking the Doctor's party not to mentioned what they had seen. He later visited her with his companions at the centre. Sherrin attempted to take him and Nyssa to an island in the harbour, but they were interrupted when they found that the locals had been infected by the crystal and were under the influence of Eldrad.
After the Doctor's TARDIS was swallowed by the sand, they got into a dinghy together. Having travelled some way, they noticed that the water was solidifying due to the crystal mass. A "quartzberg", as the Doctor labelled it, rose from its surface. Sherrin, the Doctor and Nyssa entered it to find the icebreaker Alexander within. There, Sherrin met Mulkris and learnt aboard Eldrad and his ability to restore from single parts of his anatomy.
Sherrin began to hear Eldrad's voice in her mind, as did Nyssa. The two attempted to persuade Mulkris to listen to Eldrad. After the parts of the Kastrian Mulkris had in stasis were destroyed, they regained their senses. However, Sherrin was still infected by the quartz, but this receded after the destruction of Eldrad's ring and the death of the two restored Eldrads. (AUDIO: Eldrad Must Die!)