If you remember back to Chapter 9, Trickster and Xisea went to the Oak Savannah to look for the magic plant they needed to make the antidote. They did end up at a lake! But this isn't exactly what happened at the lake. Xisea has misremembered what caused her to stop crying (it was actually Trickster saying spooky stuff!)
And finally... we get payoff to a gag from Chapter 3! Remember how Trickster kept pestering Xisea about different powers he thought she might have? Turns out Xisea does have a special power!