Meg was born to a botanist named Philip McCaffrey and Demeter in Palm Springs in California. For the first five years of her life, Meg and her father lived in Aeithales (a series of greenhouses built by Philip), but were forced to flee to New York after they were threatened by The Triumvirate Holdings (a trio of Rome's worst emperors) and Aeithales was destroyed by a member of the group, Caligula.
Sometime later Nero (another member of The Triumvirate Holdings) separated her from Phillip to raise her as his daughter. Before parting, Phillip gave Meg a rose as a gift. When Meg was six, she was disobedient to Nero, who killed Phillip as punishment, but manipulated Meg into thinking that a person called The Beast had been responsible.
Meg then spends the next six years being raised in Nero's Imperial Household. At some point, Nero gave Meg two rings that could turn into siccae blades made from Imperial Gold (a metal used by Roman demigods)
The Trials Of Apollo
In the first book "The Hidden Oracle", a now 12-year-old Meg saves Apollo (who is in a mortal for of a teenage boy) from muggers. After learning that Apollo needs to serve someone in order to eventually become a god again, Meg claims him. They then go to Percy Jackson's apartment, where Percy drives them to Camp Half-Blood, but along the way, they are attacked by Nosoi, but are helped by a Karpos which was summoned by Meg, who names the Karpos Peaches. Meg and Apollo reach Camp Half-Blood, where Meg is claimed by Demeter.
They later encounter Nero who reveals that he told Meg to lure Apollo to the Grove of Dodona, which Nero attempts to burn down. Peaches stops him whilst Meg (who begins to question her loyalty to Nero) and Apollo place wind chimes in the grove and hear a prophecy. Meg then frees Apollo from serving her and returns to Nero.
In the second book "The Dark Prophecy", Meg is sent by Nero to capture Apollo. Nero has a Germanus guard and a man named Marcus go with Meg to make sure nothing happens. However, Meg escapes them and reunites with Apollo and helps him, Leo Valdez and Calypso defeat the second member of Triumvirate Holdings, Commodus.
In the third book "The Burning Maze", Meg and Apollo battle the third member of Triumvirate Holdings, who attempts to become the new sun god by taking Apollo's power.
Meg has short dark hair and dark brown eyes. Meg's usual attire consists of black cat eye rhinestone glasses, a green dress, yellow leggings and red trainers.
- Meg is similar to Luke Castellan (an antagonist from Percy Jackson & the Olympians books, which take place before The Trials of Apollo). As both are demigods (Meg is a daughter of Demeter whilst Luke was a son of Hermes). Both were in league with an antagonist (Nero and Kronos). Both later betray their master and redeem (Meg escapes Nero and joins with Apollo whilst Luke kills himself by stabbing his Achilles Heel (his armpit) in order to destroy Kronos (who was using Luke as a host)).