When the Aurora Expedition arrives in Iceland for refuel their research ship, Captain Haddock reunites with his old friend George Chester who is then revealed to be the captain of the Sirius. Later, when the fuel available is blocked off against use for the Aurora (the ship used on the expedition to recover fragments of phostlite), Tintin and Captain Haddock decide to siphon fuel from the Sirius.
When Tintin and Captain Haddock are planning the expedition to find the treasure of the Unicorn, Haddock decides to ask Captain Chester if they could use the Sirius for the expedition.
Tintin and Captain Haddock take the Sirius on their expedition to find the remains of Red Rackham's treasure. The ship is equipped with a pump which Thompson and Thomson manually turn to supply air to Tintin, and later Captain Haddock, as they use a single diving suit to explore the wreck of the Unicorn. Bill is the ship's cook on this voyage. He blames Snowy for stealing a box of biscuits and a chicken (as he had stolen food before on the Aurora in The Shooting Star) but this time the food turned out to have been stolen by Professor Calculus, who had stowed away on board.
- The Sirius, was named after the SS Sirius, the first ship to cross the Atlantic Ocean solely under steam power, but was visually based upon the design of the John-O.88, a trawler launched in 1936. It sunk in 1941 after being attacked by German fighter planes. Hergé sketched the ship in Ostend docks before obtaining both detailed plans of the trawler from its builders, Jos Boel & Son, and a small-scale model from a collector.