"I didn't have a choice."
Ellen Clark, a.k.a. "Morpheus"[1], was a suspect in William Cochran's murders, who appeared in The Night Watch.
Background
An aspiring artist, Ellen briefly audited courses at the Glenbury College of Art and Design in Sarasota, Florida. There, she was mentored by William Cochran, an art teacher at the school. The two later fell in love and had a son named Charles. In 2007 at Nokomis, Florida, Charles wandered away from Ellen while she was painting and drowned in a nearby lake. Following the tragedy, Ellen split Charles's blanket with William and kept her half in memory of her son, with William doing the same. However, she was still traumatized by the loss, and in an attempt to cope with it, she became a street graffiti artist known as "Morpheus". Under this identity, she started tagging walls with her graffiti all across the U.S. to make political statements and stand up for the underdogs of society. At one point during her career, she had a silent partner named Corey Marlin, but she kicked him out after catching him going through her items. About two months prior to "The Night Watch", Ellen learned that a homeless woman and her son took shelter in a car in Detroit and died of overheating. As a result, she traveled to Detroit and created a makeshift memorial for the two. She used her half of Charlie's blanket as a prop, hoping that it would also serve as an appropriate commemoration of her son.
The Night Watch
After she learned that someone copied her style and abducted infant Corinne Wallace, she contacts the Detroit Police Department and has a short conversation with Hotch, where she gives him a location where he can contact her again. He goes to the location alongside Lewis, and communicates with Ellen via laptop cam. Using a distorted voice and wearing dark, hooded clothing, she reveals herself as Morpheus and offers her assistance, assuring the two agents that she is the real Morpheus because she would never hurt a child. Hotch speaks about the blanket they found at the second crime scene, which they realized was from the same blanket found at her memorial to the homeless mother and child. Ellen abruptly becomes angry, deducing the unsub's identity through this information. Claiming that she spoke with them long enough, she turns the laptop off.
Later that day, Ellen goes onto the street, but is eventually found by William and forced into his hideout at gunpoint, having found her through Corey Marlin. He confronts her about her responsibility in their son's death and demands for her to choose between being killed by him or allowing him to kill Corinne to spare her life. Ellen refuses to make a decision, but William then threatens to kill both of them, starting with Corinne. She immediately changes her mind and chooses herself. William forces her to the roof of the building again. Whilst at the top, she tries to talk down William, deducing that he was never going to kill Corinne in the first place. He has an emotional breakdown, but affirms his intention on killing her. Hotch then appears from behind, and William drags Ellen to the edge of the roof and points his gun at her. After he sees the chance to finish his last peace of art, he throws Ellen and himself down the roof, killing both of them in the process.