Batgirl #21

THE KEY TO THE CASE IS WITHIN CASS'S MIND! There's been a murder, and the only clues are buried deep within Batgirl's memories, along with the phrase "forget me not." Now locked in a prison of her past, Cassandra Cain must uncover the killer before it's too late, but as she relives her time with David Cain again and again, will she solve the murder in time... or lose her mind completely?