Chase's many credits in film and television include Sliders, ER and Manticore, and she has lent her voice to a number of project including Starzinger and Lun Lun The Flower Girl.
"We were delighted to get Chase on board," says producer David Richardson. "It was actually Frazer Hines who suggested her - they're friends. So I dropped Chase a line, and it turned out she was heading to the UK for a convention - and we had the perfect feisty role for her in The Shadow Heart."
The Shadow Heart is the climax of a trilogy that spans three Doctors. It begins in September with The Burning Prince (Fifth Doctor) and continues in October with The Acheron Pulse (Sixth Doctor).