Candide believes that Cunegonde is dead because he thought he saw her being cut open by a soldier. When he meets the old lady she leads him to Cunegonde. He is so shocked and confused about how she survived the brutally of the soldiers. So he starts drowning her with questions because he is eager to understand how this is possible. She explains to him how she survived the brutality and how she found him. 

Why do you think the author decided to keep Cunegonde alive?  Why did he use the old lady as a way for them to meet again?