A Nuisance Call

S2 E4: Lieutenant Severide (Taylor Kinney) is anxious to implicate the serial arsonist, while Dawson (Monica Raymund) and Shay (Lauren German) get a shock on a routine call. Meanwhile, suspicions continue to point to Clarke (guest star Jeff Hephner) as the mole inside the firehouse and Molly's falls deeper into the red. Elsewhere, Mouch (Christian Stolte) campaigns for union president, with the aid of Isabella (guest star Mena Suvari), and Boden (Eamonn Walker) butts heads with Gail McLeod (guest star Michelle Forbes).