Issue: Batgirl #37
Subtitle: Thicker Than Water
Date: April 2003
Feature Characters: Batgirl (Cassandra Cain)
Supporting Characters: David Cain, Batman (Bruce Wayne), Oracle (Barbara Gordon)
Guest Appearances: N/A
Other Characters: Jill, David Sullivan
David Cain makes a special visit to Cassandra's cave to deliver a birthday present, an assassin knife. The reason behind his actions are under debate by Batman until, during a case when a father abducts his daughter from an uncaring mother, she realises that Cain was actually her biological father.
"It's a knife."
- - -
- This story occured on the 26th, Cassandra's birthday