<P> During the fourth - season episode `` Now You See Me , Now You Do n't '' , CeCe is revealed to be Red Coat . In the sixth - season episode `` Game Over , Charles '' , Drake unmasked herself as Big `` A '' , and revealed that she was born male and underwent gender reassignment surgery . In the following episode `` Of Late I Think of Rosewood '' , it is shown that Charlotte spent the subsequent five years at the Welby State Psychiatric Hospital . Charlotte is eventually released from Welby after the Liars ( minus Aria ) lie under oath and testify in favor of her release as a favor to Alison . However , Charlotte is murdered by an unknown assailant merely hours after leaving Welby . Her death fueled the rise of a new `` A '' , using the alias A.D. , who was severely adamant on avenging Charlotte 's homicide . During the sixth - season finale `` Hush , Hush , Sweet Liars '' , the Liars discover that Jessica DiLaurentis has an identical twin sister , Mary Drake , a former patient at Radley Sanitarium who is Charlotte 's biological mother . In `` The DArkest Knight '' , Mary is revealed to be Spencer Hastings ' biological mother , thus making her Charlotte 's maternal half - sister . During `` Farewell , My Lovely '' , Mona confesses to killing Charlotte after finding out that her mental health had n't improved and her intentions were to torture the Liars again . Vanderwaal further discloses that a fight broke out , ending in Charlotte being shoved against a wall . A metal rod impaled Charlotte 's cervical spine , breaking her neck and leaving a cut on the back of it . After realizing what she had done , Mona began to peel rose petals before throwing Charlotte 's lifeless body from the bell tower to make it look like a suicide . In `` Till Death Do Us Part '' , the elusive A.D. is revealed to be Alex Drake , Spencer 's younger identical twin sister . Alex believed the Liars knew who was accountable for Charlotte 's murder and was also set on physically replacing Spencer due to being jealous of the upbringing that she was able to have . She had been adopted by a wealthy British family that later abandoned her , forcing Alex to bounce around foster homes and orphanages for a large portion of her childhood . </P>
<P> During the fourth - season episode `` Now You See Me , Now You Do n't '' , CeCe is revealed to be Red Coat . In the sixth - season episode `` Game Over , Charles '' , Drake unmasked herself as Big `` A '' , and revealed that she was born male and underwent gender reassignment surgery . In the following episode `` Of Late I Think of Rosewood '' , it is shown that Charlotte spent the subsequent five years at the Welby State Psychiatric Hospital . Charlotte is eventually released from Welby after the Liars ( minus Aria ) lie under oath and testify in favor of her release as a favor to Alison . However , Charlotte is murdered by an unknown assailant merely hours after leaving Welby . Her death fueled the rise of a new `` A '' , using the alias A.D. , who was severely adamant on avenging Charlotte 's homicide . During the sixth - season finale `` Hush , Hush , Sweet Liars '' , the Liars discover that Jessica DiLaurentis has an identical twin sister , Mary Drake , a former patient at Radley Sanitarium who is Charlotte 's biological mother . In `` The DArkest Knight '' , Mary is revealed to be Spencer Hastings ' biological mother , thus making her Charlotte 's maternal half - sister . During `` Farewell , My Lovely '' , Mona confesses to killing Charlotte after finding out that her mental health had n't improved and her intentions were to torture the Liars again . Vanderwaal further discloses that a fight broke out , ending in Charlotte being shoved against a wall . A metal rod impaled Charlotte 's cervical spine , breaking her neck and leaving a cut on the back of it . After realizing what she had done , Mona began to peel rose petals before throwing Charlotte 's lifeless body from the bell tower to make it look like a suicide . In `` Till Death Do Us Part '' , the elusive A.D. is revealed to be Alex Drake , Spencer 's younger identical twin sister . Alex believed the Liars knew who was accountable for Charlotte 's murder and was also set on physically replacing Spencer due to being jealous of the upbringing that she was able to have . She had been adopted by a wealthy British family that later abandoned her , forcing Alex to bounce around foster homes and orphanages for a large portion of her childhood . </P>
when do they find out about alex drake
when do they find out about alex drake
In `` Till Death Do Us Part ''
In `` Till Death Do Us Part ''