All 22 SEASON FOUR EPISODESDr. Will Halstead (Nick Gehlfuss) balances the stress as the ER's supervising attending physician with his complicated relationship with Dr. Natalie Manning (Torrey DeVitto), an attending physician in emergency paediatrics. Newly remarried, Dr. Daniel Charles (Oliver Platt) remains the Sherlock Holmes of psychiatry. Former Navy flight surgeon Dr. Ethan Choi (Brian Tee) brings his battlefield skills to the front lines of Chicago's busiest ER, the go-to place for victims of the city's gun violence. Work and home life intersect with him and April Sexton (Yaya DaCosta), a smart, bold and intuitive nurse with the ability to adeptly tackle the most harried of circumstances in the hospital. Sharon Goodwin (S. Epatha Merkerson), the venerable head of the city's largest hospital, is under intense fiscal scrutiny to preserve the bottom line while continuing to ensure that all patients receive nothing short of quality care and compassion. Maggie Lockwood (Marlyne Barret