Looking back at the book, Owen and Leigh contributed to Courtenay's abduction by withholding information from Mike and Maggie. Leigh attempted to keep Courtenay ignorant of the harsh realities of the world, and, although Maggie and Mike tried to surreptitiously give their sister vital information, it didn't include the important fact that, sometimes, strangers do know your name, and that doesn't mean they can be trusted. Owen's mistake is not as obvious but at least as damaging: had he let Mike and Maggie know that their birth mother was dangerously insane from the beginning, they would have known to censor information they gave to her about the family, such as the fact that Owen and Leigh were finally taking their honeymoon to the Caribbean, leaving Mike and Maggie alone with Courtenay.
