Having thwarted Professor One-Zero's plans in the previous book, the coding trio are shocked to discover that Professor One-Zero has now taken over the school, and has now introduced a chemistry class to manufacture the chemicals that the Professor will use to take over the world.

The trio is forced to use the last resort left to them: a letter that guides them to the ultimate turtle that could help them defeat the Professor. But before they can do that, they need to learn the use of repeats that will simplify code they produce that requires many repetitive steps.

In the meantime, Professor One-Zero forbids the trio from seeing each other in public. So, they have to meet in secret and discover a secret location. But the location is guarded, and they have to use their new coding skills to overcome the guards. Can they do so? Find out in the next book of the series.