I read most of the comments here and I find myself having a different interpretation of the episode.
To me, it makes total sense that Bjorn is Rollo' son, simply because of his physical attributes, minus the visage. He always seemed more impulsive than his brothers, which reminds of Rollo's berserker style. Lagertha clearly knows it and produced only a faint denial. Adultery was not unusual in Vikings culture. Bjorn was right though, he's not his true dad, and Rollo acknowledges that. Rollo's death must be close (illness, potion?) and he's trying to get his demons off his conscience.
Ivar is growing on me, really loved his character from day one despite his flaws. One thing I've noticed is that he seems to be aware now of his anger issues. During the scene where he comes in the empty house to find Lagertha missing, he starts yelling then stops, like he's trying to control his emotions. Acting is on point.
I couldn't care less about Floki. He's been on my blacklist ever since he's slain our beloved priest. RIP, he died for our sins. Floki should've died on his first visit to Iceland, which would've been ''in-character'' and a good send-off with the Gods. I hate the bearded guy even more though, glad his son renounced him.
Ivar is probably right, I can see Margrethe stabbing Hvitserk-change-side-every-episode in the back very soon. Wouldn't really mind that.
The nice bum lady is back, she's obviously been waiting for an opportunity to seduce Ivar. Didn't she first introduce herself in England while Ivar was stationed there? Anybody noticed how this is the only girl that Ivar is respectful to? She looks very innocent, which means trouble. Perhaps a spy from an unknown enemy? Ecgberth's final gift maybe?