Lagertha stabs Kalf, her betrothed, and then seals his death with a last kiss. It's a powerful and instructive scene, which tells us how loyal Lagertha is to Ragnar, and, even more so, to his prowess as a world conquerer.
It was clear to the audience, and therefore must have been to Lagertha, that Kalf intended to kill Ragnar. Since Bjorn would have been bent on avenging his father, had he not died trying to prevent what Kalf intended, Lagertha had no choice but stop Kalf in his tracks. The destiny conveyed in her sudden thrust of the knife thus made it an exhilarating scene, all but obscuring any scent of betrayal the stabbing also presented.
And it was not the only significant knife in the episode. Ivar suddenly stabs a boy he's been tussling with as part of a game, except there was nothing playful in the stab, which kills the boy. Ragnar puts a knife to much better use, as part of a strangely compelling seduction of Yidu, who significantly says she's a daughter of the Chinese emperor.
Meanwhile, there are symbolic knives - in the back - over in Paris, as that Emperor's ear is filled with tales from Gisla as well as poor Odo's mistress that he's disloyal to the Emperor. These knives will have important results for our story. A Paris deprived of Odo will be more vulnerable to Ragnar and Lagertha's attack, and will make the oncoming battle a classic duel between brothers.
England will also figure into this in some profound way, and I'm looking forward more than ever to the return of our Scandinavian Vikings to Europe.
See also Vikings 4.1: I'll Still Take Paris ... Vikings 4.2: Sacred Texts ... Vikings 4.4: Speaking the Language
And see also Vikings 3.1. Fighting and Farming ... Vikings 3.2: Leonard Nimoy ...Vikings 3.3: We'll Always Have Paris ... Vikings 3.4: They Call Me the Wanderer ... Vikings 3.5: Massacre ... Vikings 3.6: Athelstan and Floki ...Vikings 3.7: At the Gates ... Vikings 3.8: Battle for Paris ... Vikings 3.9: The Conquered ... Vikings Season 3 Finale: Normandy
And see also Vikings 2.1-2: Upping the Ante of Conquest ... Vikings 2.4: Wise King ... Vikings 2.5: Caught in the Middle ... Vikings 2.6: The Guardians ...Vikings 2.7: Volatile Mix ... Vikings 2.8: Great Post-Apocalyptic Narrative ... Vikings Season 2 Finale: Satisfying, Surprising, Superb
And see also Vikings ... Vikings 1.2: Lindisfarne ... Vikings 1.3: The Priest ... Vikings 1.4: Twist and Testudo ... Vikings 1.5: Freud and Family ... Vikings 1.7: Religion and Battle ... Vikings 1.8: Sacrifice
... Vikings Season 1 Finale: Below the Ash
historical science fiction - a little further back in time