After David leaves, Kiley steps out of the restaurant to call her mother for advice. Shortly after she returns, Mary Ellen—who is in on the experiment—arrives.
Kiley's moment of truth is here. "Mary, we have to talk to you," she says. "When we got here, David was here with someone else."
Though Mary Ellen reacts in disbelief, Kiley stands her ground. "I knew it was him because I texted him, and I saw him take out his phone," she says. "The look on his face said, 'I have to get out of here right now.'"
Finally, John Quiñones reveals the truth to Kiley, telling her the scenario was staged and that she's been a part of an experiment about cheating.