Siding is the thirteenth book of the Morphers. It concludes the two-part showdown between Rueben and Adam.
With Rueben working for Adam, the other Morphers must find a way to bring him back. Will they succeed or not?
The story begins with Rachel trying to contact Rueben She repeatedly tries calling him, but to no avail. Suddenly, the Morphers hear an explosion and investigates. They soon realize that explosion happened at a bank and notice someone there. They try to chase the mysterious culprit, but are soon intercepted by a group of news people and police officers. The four are taken into questioning, but are released due to lack of evidence as they were not able to find out the culprit. To make matters worse, there were no fingerprints found at the crime, nor were there any video evidence as the video camera were destroyed.
The next day, the group discuss on who should lead the team without Rueben. Rachel decides to lead the team, as she is the second-in-command. The four decide to walk around the city, hoping to find Rueben. Then, out of nowhere, they hear another explosion. They track the explosion which is at a power plant and notice a mysterious figure next to it. They start attacking the mysterious figure, but to their surprise, the figure is revealed to be no other than Rueben. Rueben reveals that he was the one that planted the explosives at the bank earlier. The Morphers tries to fight him, but are beaten. Rueben then makes a quick getaway.Later, the group discusses their plan on how to stop Rueben. However, they start to feel uncomfortable, stating that something is moving in their body.
Back at Adam's hideout, Adam tells Rueben that mission was a half success. He then tells Rueben where to attack next. Before Rueben could leave, Adam tells him if he has leader, to which Rueben replies to him saying that he already has a leader( which is himself). The other Morphers decide to find out what is inside their body . Nicholas morphs and soon finds out that they were infected with robotic bloodsucking parasites. Nick, however, discovers that he too is infected. They realized that the parasites had crawled into their body from the shock yesterday. Meanwhile, Rueben is at the top of the Sky Tower, but is soon confronted by the Morphers. Rueben wonders how were they able to find him. Rachel reveals that during their last encounter, Rueben dropped his tracking beacon and Noah was able to re-program it to locate him. The four then battle , but are still no match for Reuben. Reuben tries to escape, but is intercepted by Rachel. Rachel tells Rueben that he is their friend and that friends should not attack one another. Rueben tries to apologize, but is electric shocked by Adam, who tells him to keep fighting. The two then fight, but even Rachel is no match for him. Adams orders Rueben to activate the parasites, to which he reluctantly obeys.
Rueben heads back Adam's hideout, to which Adam congratulates him for successfully eliminating the Morphers. Rueben comments that it's a piece of cake. Adams asks him if he wants to rule the world together. Suddenly, the Morphers arrive at Adam's hideout who reveals to Adam that their death was a fake. Adam wonders how were they able to survive. Rueben reveals that he had made a decoy control and before he left, he switched the controls, giving Adam the decoy while he had the real one. He then deactivated the parasites in the Morphers. Adam, however, reveals that he had another control and activates the parasites. The Morphers soon start to turn white and tells Rueben to save them. Rueben tries to fight for the control, but is unsuccessful. He then turns white, telling Adam he had secretly planted the parasites into himself and that if he kills his friends, then he will lose his apprentice. Adam decides to deactivate the parasites , and is soon beaten by Rueben. Rueben also reveals that the whole thing was an act, as he pretended to betray his friends in order to defeat him from the inside. Rueben rejoins his friends and they fight a large group of Organisms, which they were able to defeat in a matter of time. The group then battle with Adam and were able to wound him, causing him to retreat, vowing that he will return someday.
The next day, after Rueben removes the parasites in the Morphers' bodies, the group celebrate their victory against Adam and were relieved that the betrayal was all just an act. Rueben congratulates Rachel for leading the team in his absence and tells the others that their battle against Adam is far from over.