Wallen typically worked the graveyard shift at the hospital, passing the time by working on homework or trading messages with Tim and Martina. While she was supervising Ryan Chappelle's blood test, the security desk called to tell her that a "clown" had arrived with a lot of balloons and a message for her. When she went to investigate, confused, Christopher Henderson switched Chappelle's blood sample with a fake, ensuring that his poisoning could not be diagnosed. Wallen returned minutes later with a bunch of "I'm Sorry" balloons, which were supposedly from her friend Tim. (Chaos Theory)
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