That sounds like the kind of chilling setup you’d see in a high-stakes drama—but taken at face value, it’s also a serious real-world situation that needs to be handled carefully.

If David is a real person and this actually happened, the priority isn’t solving it alone—it’s getting immediate help:

• Contact local police right away and report the threat and suspected kidnapping
• Do not respond directly to the sender or follow any instructions without authorities involved
• Preserve all evidence: the letter, envelope, messages, timestamps
• Try to confirm your daughter’s safety immediately through trusted contacts (school, relatives, friends)
• Avoid sharing details publicly that could interfere with an investigation

Threat letters like this can sometimes be scams or hoaxes, but they must always be treated as real until proven otherwise.

If this is actually a story or script idea, then it’s a strong and gripping premise. It sets up:

• Immediate emotional stakes (a parent in panic)
• Mystery (who sent the letter and why?)
• A race against time
• Potential twists (the threat may not be what it seems)

You could take it in multiple directions:

• A psychological thriller where David uncovers a hidden past
• A crime drama involving organized kidnapping
• A twist narrative where the “stranger” knows more than they should