When a violent home invasion turns out to be the result of adeadly batch of synthetic weed sweeping through Edgewater,Mickey and Boone race to contain the chaos. Meanwhile, Cassidyuncovers disturbing new clues in her sister'sdisappearance case.
As Station 42 battles through a relentless shift, theunexpected return of Battalion Chief Brett Richards throws thecrew off balance and forces Manny to confront his growingself-doubt.
Danny, Sarah and Lena race to stop a looming threat on St.Patrick's Day. Meanwhile, homesickness sparks a familygathering, and Lena's personal life takes a hopefulturn.
Cameo-oke: River (Bishop Briggs)/ Co-host: Kerri Kenney-Silver/Morgan Freeman (walk-on)/ Priyanka Chopra Jonas/ Anderson.Paak/ Black Girls with Green Thumbs Human Interest Story/Kelly Extra: Chelsea Handler and Retta / WIL: Backpack Dogs.