Everyone is shocked when Douglas introduces a fourth bionic sibling named Daniel who’s been living a normal life with an adopted family. Daniel later comes to the academy to meet his father, uncle, and cousins. After Daniel's bionics are accidentally activated by the Lab Rats, Donald and Douglas find out what happened they have to come clean to Daniel about his power-replicating abilities. Daniel also finds out that his cousins are actually his biologic siblings. Filled with anger, Daniel goes out for air on the beach, where Leo and him have a conversation about Douglas. Not too long after, Daniel, using Leo's abilities, accidentally causes a leak in the hydro-loop's fuel tank. After Adam and Daniel combined their powers to stop it, Douglas apologizes to Daniel for lying and Daniel decides to give Douglas a second chance.

Donald and Douglas reveal that they have built an upgrade for all the students bionics, except for Leo's. But the upgrade doesn't work on Adam, Bree, and Chase because their systems are older. Adam, Bree, and Chase are therefore left at their level, while all the students are much more powerful. Meanwhile, Daniel is brought to the Academy because he had been using his bionics in the outside world. Douglas decides to enroll Daniel at the Academy, and he makes Leo his mentor. Leo steadily tries to teach Daniel, but Daniel proves to be unteachable, so Leo gives him the upgrade as well. The students steadily start to vanish, including Daniel. Giselle Vickers, Douglas' old girlfriend, is revealed to have captured them. Daniel sends a video message to the Island, requesting help.

Giselle reveals she dug up Marcus from Douglas' old lair and rebuilt him, piece-by-piece. Marcus wants revenge on Douglas for leaving him to die. Everyone rushes Giselle and Marcus, but Marcus knocks everyone unconscious. Donald and Douglas are tied together in chairs, while Adam, Bree, Chase, and Leo are put in the chamber with the students, while Daniel is pulled out.