She was a serial killer who was murdering the athletes who were at the top of their various sports. She was originally after "The Whammer",
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but when Roy beat him in that little contest during the train stop, she switched her interest to Roy. She wanted to kill the best in the sport, and she felt Roy was, which is why he says what he does about being the best there ever was to Iris.

President Emeritus of the Neal Pulcawer Fan Club