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.
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.
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.
When a Chinese woman's daughter is held for ransom by smugglers, the detectives turn to her sister (Ming-Na) for help.
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.
