TV Guide reports that the actress will appear in two episodes as Netta, a nurse caring for a mysterious patient inside an asylum.
The character will apparently clash with Orwell (Summer Glau) when the computer hacker's investigation leads her to the institute, known as 'The Orchard'.
Douglas has previously played recurring roles on Law & Order: Special Victims Unit and Ugly Betty. A guest role on Six Feet Under also saw her nominated for an Emmy award in 2002.
The Cape will launch with a two-hour premiere on January 9. The first episode will be repeated in the show's regular timeslot at 9/8c the following Monday.