The Three Investigators’ Promise
The Mystery of The Invisible DogThe team’s public identity as investigators is tested by bizarre claims, police skepticism, and the obligation to distinguish a clever theory from proof.
increasing
Bearing strength in each event
decreasing
Questions on the Card

Questions on the Card
A declared purpose
Jupiter Jones explains that the group’s question marks represent the unknown and their interest in unusual cases. The motto promises to investigate rather than dismiss.
A standard to meet
Prentice’s story challenges the boys to act on their slogan without accepting every supernatural interpretation. Their work begins with curiosity disciplined by questions.
A Client’s Trust

A Client’s Trust
Fear acknowledged
Prentice asks the boys to stay overnight because he cannot bear to be alone. Their role extends beyond gathering clues to providing reassurance.
Responsibility accepted
The investigators return despite holiday plans and family chores. Taking the case means recognizing the human need beneath the mystery.
A Police Dispute

A Police Dispute
Skepticism from authority
Police officers suspect that Jupiter Jones has invented the phantom priest and treat the boys as children meddling in a real search. Their account is not immediately trusted.
A testable detail
Jupiter points to the missing Saint Patrick costume and explains how a burglar could pose as a statue. He answers doubt with a concrete reconstruction.
A Theory With Limits

A Theory With Limits
The crime solved
Jupiter Jones explains Murphy’s method, motive, and failed ransom scheme. The principal criminal mystery is resolved through linked physical and behavioral clues.
A mystery left open
The boys do not claim to know whether the phantom priest was Elmquist or a ghost. Responsible investigation includes recognizing where proof ends.
Ready for Another Case

Ready for Another Case
A seeming conclusion
Pete Crenshaw expects the case to be over, while Bob Andrews anticipates Aunt Mathilda Jones’s chores. Jupiter Jones is still thinking about Prentice’s unresolved problems.
The promise continues
Jupiter asks the others to stay near their telephones because he suspects more work lies ahead. The team’s identity depends on continuing to investigate when a story appears finished.
The first interview with Prentice
The evening Prentice asks for company
The night Jupiter is locked in the church
During the final discussion with Alfred Hitchcock
As the boys leave the salvage yard