To paraphrase a Kermodeism vis a vis the Danes: Swedish comedy, it's no laughing matter.
Anyway, as to Corndog's question, I am 100% convinced the thing in the fog was Ebba's set-up, I think probably without Tomas' knowledge.
Force Majeure (2014)
It is a great challenge in cinema to use the tools of the art to ask an interesting question. It is an even greater challenge to answer such a question. Force Majeure does an amazing job establishing the question, centered on a scene where a family, on holiday at a ski resort in France, witnesses a controlled avalanche while eating lunch, and as it seems it might actually put them at risk, the father runs off ahead of his wife and children. This instinctual moment, and the implications it has for both the self-perception of Tomas (Johannes Kuhnke) and how his wife Ebba (Lisa Loven Kongsli) views him, are potent, cascading drama even to those around them. There's a lot of questions of masculinity bound up in this, on one hand the image of the heroic male who puts women and children first, on the other the male of the wilds who swoops in for mating and swoops out just as fast.
I feel like there is a partial metaphor going on here, in that there is an otherwise kind of baffling sequence involving another woman at the resort who is in some kind of polyamorous relationship who faces a rather blistering line of inquiry from Ebba, who feels rather doubtful about the ability of such openness to not collapse into pain, especially for the children. Is this male instinct being questioned not actually about protecting the family in a time of danger but about his infidelity? And when another couple starts to bicker over whether the man would be braver in the face of the avalanche, is it really an argument over views of fidelity?
Monogamy is not natural enough for the majority of people to successfully practice, yet we have structured families in such a way that when this likely event occurs, we practically demand that it shatter families. It is kind of interesting to think of this film as a family holding things together after infidelity, but I'm not sure it is tight enough as a metaphor to pay off fully.
Of course, if this isn't metaphor, the results are worse as things like the discussion over the woman's polyamory seem like baffling non sequiturs. After such a rousing start, it feels a bit aimless for a large chunk of the second half, at least when it is not giving in to scenes of pretty absurdly overemotional response. I mean, when Tomas ends up in a big tent with a bunch of half-naked guys, is that some sort of reclaiming manhood voyage? When Ebba panics on the bus ride down from the mountains, is that a restoration of the proper order, where women are hysterics? When Tomas decides to accept another man's offer for a cigarette and the film closes on him proudly embracing to his son that he smokes, are we seeing smoking as the ultimate sign of secured masculinity? No, smoking give you cancer you dumb ass. The exploration of masculinity approach gets rather frightening so I guess I'll stick with the slightly frayed monogamy approach.