Christopher, Jalil, April, David, and Senna, still trying to find a way back to the Earth they know, find themselves in the parallel universe of Ireland, where they must contend with giants, leprechauns, gods, and Merlin.
When Sam asks Alison to the Valentine's Dance she is elated, until she finds out that her best friend Isabella also likes Sam and Izzy only has three months to live.
The fact that his mother has been infested by an alien parasite and his father is planning to remarry puts Marco under such stress that he begins to morph into bizarre creatures that he is afraid will attract the attention of the Yeerks.
