So Colfer pumped some volume back into the series with The Lost Colony, but how does he keep it going? By bringing back a psychotic mastermind. This novel begins after the last novel ends (clearly) and picks up with Artemis who hasn’t aged at all, but is supposedly three years older than he was due to the final trip in time during the last novel and bringing Hydras back to the current plane of existence.
This novel centers around a series of time loops which all occur as a result of Artemis attempting to keep his parents in the dark about why he hasn’t aged during his absence and to keep the underworld hidden from them. If you think about it to long you could easily get stuck in an existential quandary of whether any of the series would have happened if he did or did not go back in time or did or did not try and cure his mother.