Harlee struggles with becoming an FBI informant while Wozniak suspects every member of his crew. Paranoid that Wozniak's search will lead to her, Harlee suggests polygraphing the entire crew, a plan that backfires. An appeals case sends Wozniak to watch tapes from his first encounter with Harlee, revealing a dark secret from their past. Meanwhile, Espada helps Tess deal with her husband's infidelity.