As they grow closer, Mark finally plucks up the courage to casually ask Susan out, however she declines, telling him that they "need to talk". Shortly after, Mark witnesses Susan in numerous secret talks with the ER's chief of emergency medicine, David Morgenstern, and concludes that they are seeing each other. He confronts Susan, but she reveals that Morgenstern was merely helping her to transfer her residency. Desperately missing her niece, Susan had made the decision to move to Phoenix to be near her sister's family.