Cathbad and Deidre tell Ivar how as young boys Ronan and Angus played with the druid's magic powders, awakening the Gray Man, a powerful spirit who, angered at his slumber being disturbed lay a curse on the castle of Kells.
Rohan and Deirdre work to clear Angus when he's accused of robbing villagers and vandalising their properties. While Ivar is busy looking for the real culprit, Maeve summons a fire monster and sends it to Kells.
Tricking Cathbad into turning him human-sized, Mider overthrows Maeve and becomes ruler of Temra. Realizing the fairy is a more dangerous threat, the Knights aid Maeve in taking back her throne as the answer to King Fin Varra's advice.
Ivar manages to steal back his people's chalice. However, the chalice is Mider's link to the dark realms and taking it back to Ivar's kingdom is too dangerous. Ivar decides to take the chalice anyway but is captured by Maeve.
In order to stop a storm of dark magic, the kings of Kells and Tir Na Nog must switch places for a day. While Conchobar organizes the fairies into a fighting force, Fin Varra's more fun ways with the Kells soldiers leave them vulnerable.
A beautiful princess named Lynette is found on the shores of Kells without her memory by Fin Varra's scouts. Garrett grows closer to her while her arrival coincides with the monstrous Grindon attacking.
Lugad helps turn the tide of war for Temra as the Knights must figure a way to stop him. Rohan undergoes a dangerous test to gain the powerful Battle Fury armor.