After seven years, Pretty Little Liars concluded this week and all was revealed about AD - but just who were they?
Well it turned out that AD was a new character - but we had seen her before in recent episodes.
AD was Alex Drake, Spencer's 'evil twin' who had been given up for adoption in England at birth.
Neither she nor Spencer knew about one another until Wren bumped into Alex in England some years back, mistaking her for Spencer.
Wren and Alex then fell in love as he told her all about her half-sister Charlotte (CeCe, aka A), twin sister Spencer and the Liars.
Charlotte and Alex met up previously when the former fled to France after killing detective Wilden where they formed a close bond.
Five years later and on learning of Charlotte's death, Spencer came to Rosewood for revenge.
Oh, and she killed Wren and turned his ashes into a necklace, something which is sort of glossed over very quickly.
In the season finale, we learned how at times Alex had been impersonating Spencer over the previous few episodes before kidnapping her along with Ezra (for reasons unknown).
With help from Mona, Jenna and a horse (seriously), the Liars eventually tracked down Alex's lair and rescued the pair but not before a cliche 'No, I'm the real Spencer!' stand off.
In one last twist, we were led to believe that Alex and her mum Mary Drake (who was sort of in on it) were taken away to prison when in fact they were captured by Mona and locked up in her doll house in France - obviously.
The very last scene of Pretty Little Liars teased a potential spin-off, re-creating the very first episode as a new group of Liars were seen having a sleepover.
They awoke to find Alison's school student Addison Derringer missing after hearing a scream, mirroring Alison's original disappearance.
Pretty Little Liars is available on Netflix in the UK.