Alexis "Lexi" Glass-Mason was a main character and Tom Mason's and Anne Glass's daughter, and half-sister to Hal Mason, Ben Mason and Matt Mason.
In season 3 Alexis was only a newborn, however advanced early on, which was discovered to be caused by alien DNA. Alexis was captured when Anne left Charleston with her, and at the end of season 3 she is found by Tom, and she has aged rapidly. Another sign of alien DNA was when she caused all of the eye-worms to be released from Lourdes Delgado.
22 days later, at the beginning of season 4, the 2nd Mass is split by the Espheni. She is protected by Ben Mason, and has aged physically to the age of a 21 year old. Alexis has been protecting the location of Chinatown, and communicates with the Espheni who teach her to control her powers. At the end of season 4, she sacrifices herself and destroys the Espheni Power Station.
As Tom gets closer to an attack on the Espheni Queen, the Espheni create a clone of Alexis and send her to assassinate Tom. She is found by her brother Matt and taken to the base where she reveals important information about the Espheni plan before attacking her father. The clone is killed by Ben with the Dornia Weapon.
