While working the murder case of an undercover ATF agent, McGarrett and the Five-0 team are tasked with watching Mary’s newly adopted baby after she gets sick.

Five-0 is set up when a bad tip leads them to an abandoned building that is rigged to explode with McGarrett and Danny trapped inside.

While Five-0 hunts for a notorious criminal who has never been seen, Kono must fight for her life when she discovers the villain's identity. Also, Kono confesses to Adam that she's conflicted about their future together because of his ties to his formerly corrupt family business.