One night in the Nemedian municipality of Numalia, the second largest city of Nemedia, Conan enters a fantastic establishment: a great museum and antique house which citizens call the Temple of Kallian Publico.
In the midst of robbing this museum, Conan finds himself embroiled in a murder investigation when the strangled corpse of the temple's owner and curator, Kallian Publico, is found by a night watchman. Though the Cimmerian is the prime suspect, the investigating magistrate, Demetrio, and the prefect of police, Dionus, show remarkable forbearance. The two allow Conan not only to remain free, but also to keep his unsheathed sword while their nervous men search the shadowy premises. It was a combination of Conan's massive physique, the fiery glare in his eyes, and the insistence that he'll disembowel the first person who tried to apprehend him which kept the royal guards at bay.
As his on-scene investigation unfolds, the magistrate soon learns from Promero, Publico's clerk, that Publico had received from distant Stygia a strange bowl-like sarcophagus which now lies unsealed, open, and empty. This sarcophagus was said to be a priceless relic found among the darkened tombs far beneath the Stygian pyramids and sent to Caranthes of Hanumar, Priest of Ibis, "because of the love which the sender bore the priest of Ibis". Intercepting this rare item meant for Caranthes, Publico had believed the sarcophagus contained the fabled diadem of the giant-kings whose primordial kin dwelt in that dark southern land before the ancestors of the Stygians arrived. However, the object contained within was never the diadem, but something of a more insidious nature.
While the magistrate and his men are baffled when uncovering this aforementioned information, the reader quickly begins to suspect
the murderer may have been something other than entirely human and was contained within the now-opened sarcophagus.
An inhuman scream forces the police to retreat from the museum, leaving Conan to fend for himself with the roaming "murderer". Soon, Conan eventually locates the culprit whom he hesitantly dispatches with his long sword.