The setting of the rescue is also important. Is it in a dark, dangerous forest? Or perhaps in an ancient, crumbling castle? The setting can add to the atmosphere and the challenges Percy has to face. If it's in a forest full of monsters, he'll have to fight his way through them to reach Bianca and Zoe.
The relationship between Percy, Bianca and Zoe should be well - developed. If Bianca and Zoe have some sort of special connection to Percy, like they once saved his life, then it makes his act of saving them more meaningful. Also, how do Bianca and Zoe react when Percy comes to their rescue? Are they grateful, or are there some underlying tensions that surface during the rescue?