Alexandra “Alex” Drake is a fictional character created by I. Marlene King and portrayed by Troian Bellisario in the American television series Pretty Little Liars.

Officially introduced in the series finale, Alex Drake is both the identical twin of main character Spencer Hastings and the previously anonymous identity known as "A.D." In childhood, Drake was adopted by a wealthy British family that later abandoned her, forcing Alex to bounce around foster homes and orphanages.

However, by the end of the sixth season, Marlene warned Bellisario they were staying true to the plan, so they began working on the character's history and characteristics.

"[3] Referred to as the series' "ultimate villain,"[3] Alex is an "Essex girl"[4] whose portrayal was influenced by late singer Sid Vicious.

Mary later gave birth to identical twins at Radley Sanitarium, a mental institution where she was frequently a patient.

The oldest child, Spencer Hastings, was taken from Mary (much like her first born Charlotte) and placed in the care of Peter and his wife, Veronica.

[5] Mary, desperate to escape Radley, allowed Doctor Cochran to arrange Alex's adoption in exchange for $500,000 and a resignation from the psychiatric hospital.

In the season and series finale, "Till Death Do Us Part," a year has passed since A.D. went under the radar after discovering Mona Vanderwaal as Charlotte's killer.

It is implied during the first episode of Pretty Little Liars: The Perfectionists that Alex and Mary escaped from Mona's dollhouse and are now on the run.

[6] The character's introduction and subsequent reveal as the series' final antagonist was met with a deeply polarizing response.

Moreover, Troian Bellisario's performance also faced mixed reviews, with her attempt at a British accent being singled out for criticism.

"[7] Yana Grebenyuk of TVFanatic echoes the same sentiments of praise, writing that "Alex delivered above and beyond what a Spencer twin could have actually turned out to be.