Catherine was a mortal woman, who appeared to be Bert Myers devoted girlfriend.
She put up with his distraction during the Cloak and Dagger affair, and though she threatened to leave, did not. Bert told her that she was the best thing that had happened to him, and that he loved her. He promised to take her away on a trip and that his work would never again come between them.
The reality, however, was far different. Catherine was, in fact, an agent put in place by Ludwig Weiss, and Bert was her assignment. Bert was going to be ordered to kill a client who had hired his security firm. Catherine was there to complete the assignment should Bert, or a secondary backup in place, fail.
When her role was discovered, she tried to run for it, but Bert cornered her, and held her at gunpoint, on the verge of killing her for her betrayal, "What a lie it all was."
She responded, "Not all of it. C'mon, we had some fun. The sex was great. Don't take it personally."She then told him if he let her go, she would provide him with the Stazi file on him that Ludwig had, that if he killed her, that would still be out there, so essentially, if she died he died.
Nick arrived at that point, and tried to talk Bert down, telling him it wasn't worth destroying his life just for revenge. Bert thought it might be, but Nick prevailed, and Bert lowered his weapon.
Catherine was later linked to the murder of a police officer, and went to prison.