Voight learns from a poker buddy that his son is in town and didn't tell him.
Voight gets called to a crime scene and finds a baby dead in a duffel bag.
Roman and Burgess arrive at Chicago Med and find the doctors working on the baby, who is actually alive. They find out the baby has sickle cell disease.
Ruzek finds a possible suspect with sickle cell. Ruzek and Olinsky question him. His DNA matches the baby. He swears he knows nothing about the baby and didn't hurt her.
He helps them identify the baby's mother. Lindsay and Halstead question the girl's parents.
The father tells them that their daughter gave the baby up for adoption, but there's no paperwork on it. He gives them the name of the midwife who helped deliver.
The midwife gives Olinsky and Atwater the information of the family who adopted the baby. The couple tells them the baby was never brought to them.
The baby's mom arrives at the station and tells them her parents made her give up the baby.
Voight tells Lindsay that Justin was a twin, but the other baby was a still born.
They arrest the couple that adopted the baby. The dad admits he fell asleep outside with the baby and he panicked when she didn't wake up.
The couple's son tells Ruzek he took the baby outside.
The baby survives and her birth mom wants to keep her.
Burgess and Roman sleep together.