When the boys grew up, they went to Zealand, and were bidden by their friends to avenge their father. They vowed that they and their uncle should not both live out the year. When Ragnar found this out, he went by night to the palace, prompted by the recollection of his covenant, and announced that he was come privily to tell the king something he had promised. But the king was asleep, and he would not suffer them to wake him up, because Frode had been used to punish any disturbance of his rest with the sword. So mighty a matter was it thought of old to break the slumbers of a king by untimely intrusion. Frode heard this from the sentries in the morning; and when he perceived that Ragnar had come to tell him of the treachery, he gathered together his soldiers, and resolved to forestall deceit by ruthless measures. Harald's sons had no help for it but to feign madness. For when they found themselves suddenly attacked, they began to behave like maniacs, as if they were distraught. And when Frode thought that they were possessed, he gave up his purpose, thinking it shameful to attack with the sword those who seemed to be turning the sword against themselves. But he was burned to death by them on the following night, and was punished as befitted a fratricide. For they attacked the palace, and first crushing the queen with a mass of stones and then, having set fire to the house, they forced Frode to crawl into a narrow cave that had been cut out long before, and into the dark recesses of tunnels. Here he lurked in hiding and perished, stifled by the reek and smoke.