find a length of rubber pipe stained with soot. At the inquest, the doctors and police reveal that Paul was killed by carbon monoxide inhalation, the pipe having been used to connect the exhaust of Mike's car to the vault ventilator. A neighbour testifies she heard the car running in the garage from six to nine on the night Paul disappeared. Mike says he was out walking the streets until eight, and that around nine had started the car to warm it up by running the engine for a few minutes before going for a drive. Gina's housekeeper speculates too freely about her mistress's relationship with Mike, and at the end of the inquest Mike is arrested for the murder. Campion befriends Ritchie, an odd and rather awkward cousin - the brother of the vanished Tom, and with his help questions Miss Netley, Paul's suspicious secretary. He tracks down Paul's mistress, but finds she knows nothing, except that he missed an appointment with her on the night he died. He learns of a valuable unpublished manuscript of a play by William Congreve owned by the firm and regarded as a financial asset, which Paul had hoped to display, and of a visit Paul paid to a London district on business concerning a key. From his manservant Lugg, he learns that a renowned underground key copier lives in the area mentioned, and together they investigate, Lugg's criminal past helping to persuade the man to help by providing a copy of the key he made for Paul. Campion visits the Barnabas offices with Ritchie's help and finds someone in the vault. They fight, and Campion subdues the man, who turns out to be the accountant, Rigget. Rigget confesses to having made a copy of the vault key and sneaking in at night to look for any valuable information. On the night after Paul's death, he had also entered the room and found Paul curled up and dead in a corner, and the vault unlocked; he locked it using Paul's key. He also took the vault key from inside the door, locked it on the outside when he left, returning the key to its normal place. The trial begins the next day, and Campion, exhausted from his long night, attends. Things look bleak for Mike, but Campion has found out from an uncle working at the British Museum that the document in the