|"Lesser of Two Evils"|
|Season 4, Episode 06|
|Air date||October 31, 2018|
|Written by||Safura Fadavi & Meridith Friedman|
|Directed by||Martha Mitchell|
"What You Don't Know"
"The Poison Inside Us"
Dr. Manning and Dr. Halstead become skeptical of a patient's injuries when the victim of a car accident is brought into the hospital. Ethan and April have a difficult time understanding Emily's attachment to her boyfriend despite recent developments. Will and Natalie brace for their joint bachelor/bachelorette party.
- Brian Tee as Dr. Ethan Choi
- Colin Donnell as Dr. Connor Rhodes
- Marlyne Barrett as Maggie Lockwood
- Nick Gehlfuss as Dr. Will Halstead
- Norma Kuhling as Dr. Ava Bekker
- Oliver Platt as Dr. Daniel Charles
- S. Epatha Merkerson as Sharon Goodwin
- Torrey DeVitto as Dr. Natalie Manning
- Yaya DaCosta as Nurse April Sexton