Tani and Junior go under cover as prospective parents to infiltrate a private school where the headmaster was murdered; Adam's life is on the line when he is held captive and forced to produce a massive amount of money.
Mac participates in a challenge to create robotic combat machines; Mac must help a competitor when her vehicle is hacked and heads for the Pentagon; Jack attends his high school reunion.
McGarrett and Danny investigate the murder of a private detective whose client was killed the same way; Adam sends Jessie into a dangerous situation with disastrous consequences; Danny's uncle comes to town to help with the restaurant.
Neela finds out the aorta surgery on Sheryl Hawkins (Aida Turturro) has caused an infection; Abby discovers a serious condition while treating a beaten teen; Kovac struggles to forgive Abby for her indiscretion.
Tony receives news that impacts his and Jane's futures; Parker and Kim get closer outside of the law office; Grayson decides to sell the house he shared with Deb.
