As Leo struggles to come to terms with being human, Mattie takes him back to the Hawkins' home, where a surprise night out allows them to confront their feelings for each other. Laura is determined to uncover the truth about the too-secret Operation Basswood and tries to enlist Dr. Neil Sommer's help, only for things to take an unexpected turn. Joe reluctantly decides to help Karen with Sam, and Niska receives a mysterious message.