Prove It

S2 E2: In the wake of Heather's (guest star Chaon Cross) incident, Lt. Casey (Jesse Spencer) is having a hard time handling his newfound responsibilities. Lt. Severide (Taylor Kinney) is on edge dreading the next attack from the firehouse’s arsonist. Meanwhile, with Renee (guest star Sarah Shahi) back from her mother's, Severide knows he has to confront her about his paternity suspicions. Elsewhere, Mouch (Christian Stolte) begins his campaign for union president and Shay (Lauren German) and Dawson (Monica Raymund) feel that they need to get out more.