Deadly question

If you mean in this particular book then it is Ali and Nick who we discover is 'Helper A' and was known to the girls as different people.

JUST IN CASE YOU DIDNT READ IT YET! CONTAINS THE IDENTITY OF A!!

The A's were revealed in Deadly as Ali and her boyfriend, Nick/Tripp/Olaf/Derrick/Phineas. I dont know where she is going with this if everyone knows who A is

In book 4 it was Mona. Then in book 8 Ai decided to follow in Mona's footstep. Now we are trying to figure that out!

~Spoilers~

Actually.. If you read Ali's Pretty Little Lies, you'll find out that Ali planned the whole A thing even before Courtney was killed...