Frothi inherited his father's kingdom; but Ali, his half-brother, who was a great warrior, conquered Sweden. Frothi's men feared Ali and persuaded Frothi to try to have him put to death. Frothi yielded to their entreaties, and Starkad, the famous warrior, was dispatched to perform the deed. When an opportunity presented itself, he stabbed Ali to death. "My brother has caused this," said Ali, and died laughing.
Later, Frothi defeated Jorund, King of Sweden, and made him a tributary prince. He also defeated Swelling, a Swedish duke, and treated him in the same manner. Frothi abducted Jorund's daughter, by whom he had a son who was called Halfdan. But taking another woman to wife, a legitimate heir was born to him, and this son was called Ingjald.
Starkad, however, was so filled with remorse for having killed Ali that he did not wish to remain with Frothi. He went, therefore, soon after to Russia and later to Sweden, but, disgusted with the idolatry of the Swedes, returned to Frothi. Ingjald, son of Frothi, had in the meantime married the daughter of Swerting, thus, as it seemed to all, effecting a reconciliation with him.
Jorund and Swerting, however, formed a conspiracy against Frothi, and he was slain one night while sacrificing to the gods. In the meantime, Starkad was absent in Sweden, where, under the guise of friendship, he was detained by gifts, in order that the plot against Frothi might be the more easily executed.
Swerting placated Ingjald, Frothi's son and Swerting's son-in-law; but Halfdan, Ingjald's half-brother, conquered Skåne and avenged his father's murder by putting to death Swerting's twelve sons, who had slain Frothi. At the instigation of Starkad, Ingjald put his wife, Swerting's daughter, aside. He also granted Halfdan a third of the kingdom. Swerting's daughter later bore Ingjald a son (Agnar); and by his wife, Sigrith, Halfdan had a daughter, Signy, and two sons, Hroar and Helgi.
Ingjald, however, desiring to rule over the whole kingdom, fell upon Halfdan unexpectedly with an army and slew him. He married Halfdan's widow, and by her had two sons, Hrörik and Frothi. Signy grew up under her mother's care, and later Ingjald gave her in marriage to Sævil, an earl in Seeland. But Hroar and Helgi hid from the king on an island near Skåne, and when they had arrived at the proper age they slew Ingjald and thus avenged their father's death.
Hroar and Helgi now became Kings of Denmark. Later Hroar married the daughter of the King of England. Hrolf, nicknamed Kraki, who was eight years old when his father, Helgi, died, succeeded him on the throne. Hroar was soon after slain by his half-brothers, Hrörik and Frothi. Hrolf then became sole King of Denmark.[160]
The story in the Bjarkarímur is substantially the same as the story in the Skjọldungasaga. Both are plainly based on the same account, and, within certain limits, are identical with the corresponding story in the Hrólfssaga. Skåne, mentioned in the Skjọldungasaga in the phrase "in insula quadam Scaniæ," is not mentioned in the Hrólfssaga. Its insertion in the Skjọldungasaga is due to the fact that Halfdan, the father of Hroar and Helgi, is said to have conquered Skåne, and, as a result, would be regarded as having ruled there. But its presence in one account and omission in the other involve no contradiction. In all that belongs peculiarly to the story about Hroar and Helgi, the account in the Skjọldungasaga is identical with the account in the Hrólfssaga. According to both sources, the name of the boys' mother was Sigrith; their father's name was Halfdan; he was slain by his brother, who fell upon him unexpectedly with an army; the fratricide married the murdered man's widow; Signy was the sister of Hroar and Helgi; she married Sævil, an earl in Denmark; Hroar and Helgi had to conceal themselves on an island to save their lives (according to the Bjarkarímur, they were brought up by the old man Vifil, a circumstance omitted in the Skjọldungasaga, but contained in the Hrólfssaga); when they had arrived at the proper age, they slew (according to the Hrólfssaga and the rímur, "burnt-in") their father's murderer and thus avenged their father's death; Hroar and Helgi then became Kings of Denmark; Hroar married the daughter of the King of England; Helgi's son was Hrolf, who later became sole King of Denmark.
The essential difference between the story as it is in the Skjọldungasaga and as it is in the Hrólfssaga is that, in the Skjọldungasaga, Ingjald is said to be the brother of Halfdan; while in the Hrólfssaga, Frothi is Halfdan's brother. The Hrólfssaga has, however, preserved the earlier account. The Skjọldungasaga dates from about the year 1200.[161] About the year 950, Frothi is said to be the slayer of Halfdan;[162] and in Historia Regis Waldei, Frothi is made the typical villain in a Hroar-Helgi type of story[163] (the "exile-return" type), so that, in the version of the story that was current in England, Frothi must have been the slayer of his brother. The conflicting statement that it was Ingjald who slew Halfdan requires, therefore, an explanation.
In Saxo's Gesta Danorum, the story about Hroar and Helgi is told twice. It is first told in the second book, where we find the version with which is connected the story about Hrolf Kraki, Yrsa, Athils, and Ingjald and his son Agnar, whom Bjarki slew; it is told a second time in the seventh book, where Hroar and Helgi are called Harald and Halfdan, and where the story about them is another version of the same story that we have in the Hrólfssaga. Not only do Hroar and Helgi appear (disguised under different names), but Frothi and Ingjald again appear.