Carissa is a woman with long, dark hair and brown eyes with pale skin. As a professor, she wears corporate casual attire or possibly a lab coat, depending on what she teaches.
While she was Professor Gellar's teaching assistant, she worked with him on a Lamb ritual where she posed naked with a dead lamb on her head. She developed a sexual relationship with the Professor until she discovered that he always did this with his assistants. After they broke up, she earned her doctorate and became a professor herself, working in a Tallahassee University.
She is first questioned by Detective Joey Quinn and Sergeant Angel Batista regarding Gellar's connection to the Doomsday killings. She firmly says that Gellar cannot be connected to these killings in any way. She is even willing to help them find him just to prove that they have the wrong man.
Quinn and Batista decide to head back to Miami the next day. Quinn meets Clarissa at a bar and they spend the night together. In the morning, Batista goes to pick Quinn up and Carissa opens the door and lets him in. While waiting, Angel finds a book of Gellar's in a box and calls Clarissa into the room. At first, she is furious at him for going through his stuff but changes her tone when she sees the similarities between his drawings and the killings.
After it is discovered by Miami Metro Homicide that Clarissa is the one in a newspaper photo helping Gellar with his Lamb ritual, she is called in by Lieutenant Debra Morgan for more information. Quinn avoids her, and she is questioned by Sergeant Batista while Debra watches through a two-way mirror..
During the questioning, Clarissa grows uncomfortable and reveals no new information. Debra orders Quinn into the interrogation room to assist Quinn. Due to Quinn's unfriendly attitude, Clarissa eventually blows up. She mentions her night with Quinn and states that they are to leave her alone or she will sue the department. Then she storms out of the building. An enraged Debra confronts Quinn about his sleeping with a witness.