When Olivia's best friend goes missing, she and Wallace team up to put together the pieces of the puzzle. Olivia realizes she can hear something no one else can - even without her hearing aids. Could it be the Piper's song?

Painful memories threaten to shut down Olivia's search for the missing children and now - her best friend. Can she overcome them in time to save Wallace from the trap he's walking into?

Realizing Olivia can communicate with the possessed children, she and Wallace come up with a plan to rescue Marcus. Can they reach him before it's too late?