In The Bird That Died of Diamonds, Pierre Pastor was the sixteen year old son of the maid of the Countess Castelano who lived in a villa on the Riviera. Pastor becamse suspicious of a Baron Zorrall when he began to romance his mother. Pierre could not understand why a rich man would be interested in an elderly widow. As it turned out, Zorrall was an international jewel thief. He using Pastor's mother to gather information about the household and the movements of the Countess in order to plan a theft of the Countess's jewels. When the jewels were discovered stolen and Zorrall fell under suspicion, naturally Pastor's mother also became implicated.
Pastor had followed Zorrall and had seen his gun cases being taken to the station and consigned to an address in Scotland. The next day he also saw Zorrall's luggage being sent to the Crestata Hotel in London. Pastor knew where his mother kept her money and so took some to travel to London, intending to retrieve the jewels and clear his mother. He met and confronted Zorrall at the Crestat Hotel and demanded that he return the jewels. Zorrall had started hitting him whereupon Pastor had grabbed a knife to stab Zorrall, killing him. He did not find the jewels in the hotel and so returned to France.
Zorrall had earlier stuffed the stolen jewels into shotgun cartridges which he then sent along with his guns to Tomlecht, the Scottish estate of Colonel Colin McGill, where he had made arrangements to spend a season hunting as a paying guest. Zorrall had planned to meet up with his loot in Scotland but naturally, he never turned up. The stolen jewels were subsequently discovered by Colonel McGill when he had borrowed some of Zorrall's cartridges to shoot a pheasant and had ended up biting into a diamond. When McGill turned the jewels over to Scotland Yard, they were identified as belonging to the Countess and linked to the murder of Zorrall at the Crestata Hotel. Biggles theorized that Zorrall's murderer might be an accomplice in the theft and might still be interested in retrieving the jewels. An advertisement was thus planted in shooting magazines for Zorrall to collect his guns from Tomlecht to serve as a bait. Pastor saw the advertisement and realized Tomlecht might be where the Zorrall had sent the stolen jewels. He made his way to Tomlecht, only to find himself walking into the trap Biggles had set. Caught, Pastor told Biggles the whole story. He was subsequently tried for killing Zorrall but a court ruled that he was acting in self-defence and he was discharged.