Spoilers ahead! Scroll down at your own risk.
In what is now known as the "year 0", a boatful of refugees arriving in Spain brought an unknown contagious disease with them that was called "the Rash", after what was thought to be its main symptom. Governments the world around pondered to take countermeasures so as to avoid the cost of having their workforce incapacitated for a couple weeks - and few did. By the time it became clear that infected were in for coma, death, and worse, the time to prevent the spread of the Rash had already passed.
In the comic's present time, the year 90, the leftovers of the five largest Nordic countries have re-established contact with each other, but are oblivious about the state of affairs elsewhere in what is now called "the Silent World". Iceland, which did implement and enforce national isolation in time, is the largest "safe area" in the Nordics and houses almost 80% of the remaining population - in spite of having lost about one third of their year 0 headcount as well.
"The Rash" has apparently continued to evolve into "the Illness", which fills the Silent World - including most of the former territory of the other four Nordic nations - not only with the possibility of infection and death, but also murderous monsters that are the result of animals and humans (un)lucky enough not to have died after infection. The percentage of humans who have immunity against the Illness is rising, but encounters with monsters lead to fights to the death for all unfortunate enough to meet with them. A special branch of the military, the cleansers, works on winning back habitable areas from the bestiary.
Overcoming reluctance on the part of the government, a group of four organizers has obtained permission to finally send an expedition into the Silent Lands, though the actual purpose of the endeavour is to obtain antiquities - books, to be precise - to sell and gain a fortune with. The task of actually putting their lives on the line has, naturally, been handed to someone else - five adventurers selected for the specific purpose of being a cheap, expendable workforce.
Leaving the Known World by way of the Öresund bridge (which broke in the process), the expedition started checking libraries in Kastrup, a suburb of the former Danish capital of Copenhagen. So far, the results are mixed, and not quite up to expectations, and a mishap that took place while the team tooled up forced them to interrupt book-scavenging and deal with an unexpected lack of rations.
Another series of mishaps then hands them only a small amount of food, and a sixth mouth - a civilian stowaway - who has no more choice left but to stick with them, likely for the entire length of the mission. Furthermore, a run-in with ghosts, which proved to be more dangerous than ever expected, forced them to leave Copenhagen prematurely.
The expedition is now headed to the Odense University Hospital (OUH), which had provided some novel drug to Copenhagen back in Y0. It is unclear whether it was meant as a cure, a vaccine, or even something else, much less how it obviously failed to stop the apocalypse. On the flip side, the cross-country trek allowed the crew to fill the cat-tank's cargo hold with a satisfying loot of books ...
Memes, Plot Points and Running Gags Edit
Apart from characters' individual traits, there are a couple character-spanning topics that appear repeatedly. First and foremost, the five nations still have their individual languages, and the ensuing communication barriers certainly help them keep their old preconceptions about each other - as well as the occasional new one.
Another recurring topic is the ancestry of the protagonists, more precisely, how they are descendants of the various characters that appeared in the prologue.
A central topic in the making - now that the expedition has left the Öresundsbro Base and entered the Silent World - is the "Cat-Tank", the expedition's mobile base of operations (and, presumably, shelter from the ubiquitous dangers).
Heart shapes have appeared quite a number of times in the comics, from Mr. Pedersen's tie in the prologue to the Lumilintu's decor to jewelery on the giant attacking the Dalahästen to Cthulhund's collar, the latter two leading to speculation that Cthulhund was a pet of the woman who brought said jewelery into the giant. Another theory is that the symbol has been inspired by the Danish coat of arms, but note that only half of the appearances (Mr. Pedersen and Cthulhund) are related to Denmark.