Teddy Jo and the Kidnapped Heir by Hilda Stahl

Teddy Jo looked out the window of the speeding car, her heart racing in fear. This was like a nightmare come true -- she had been kidnapped! And with Serlo Sprague, of all people! Serlo was very rich, so Teddy Jo figured the kidnappers must want some money from Serlo's father. Teddy Jo had been with Serlo, so they had grabbed her, too. Where were they going? Even if she and Serlo did escape, would they be able to find their way home? Maybe she'd never see her family again!