PERHAPS being old, Philip Larkin once surmised, "is having lighted rooms/ Inside your head, and people in them, acting." At 82, Sheldon Horowitz has all of this going on, and more, as he finds himself on the run with a traumatised six-year-old boy in a country he scarcely knows.

Horowitz, a New York Jew, widower, and former Marine who saw action in Korea, has not long begun a new life in Norway, courtesy of his granddaughter Rhea and her husband Lars. He is cranky and outspoken; Rhea would not be surprised to learn that he has dementia. But privately he is haunted by memories of his son Saul, Rhea's father, who followed him into the US army and was killed in Vietnam. Inside his lighted rooms he relives his days in Korea (he was a sniper there), visualises himself in Vietnam alongside Saul and his comrades, and has conversations with Bill, an old friend from his New York days. Horowitz does indeed have, as he says at one point, a rich inner life. Rhea, who suspects that her grandfather is talking increasingly to the dead, nevertheless accepts that he still has all of his powers of reasoning.

One day the old Marine is witness to the murder of a woman who lives upstairs. The murder is a messy hangover from the Balkan wars. On impulse – he can't be sure that the Norwegian cops will not just hand the boy over to the "monster upstairs" – Horowitz decides to flee with the woman's son, whom he christens Paul. Needless to say, they do not speak a word of the other's language; the boy barely utters a word throughout.

Despite his age, his unfamiliarity with his adopted country, and the fact that he really has no plan other than to keep the boy safe for as long as he can, Horowitz, summoning up the lessons drummed into him during his military training, manages to remain one step ahead of the Norwegian cops and also of the Balkan gang who are on the trail of the boy. The climax, when it comes, is finely judged.

In the hands of Derek B Miller, a Boston-raised academic who now lives in Oslo with his family, Horowitz is an intriguing creation. He was, it turns out, a secondary character in an as-yet-unpublished book by Miller, and something about him stayed in the author's mind. Early on, the old Marine puts you in mind of Clint Eastwood's character in Gran Torino – like him, an elderly Korean War vet and a widower – and it's not a stretch to imagine Eastwood playing Horowitz in a film version. But the book is also, in part, a moving, well-written meditation on the ageing process, on memories and regrets. We see Norway through a stranger's eyes, too (indeed, the book was first picked up by a Norwegian publisher). It's a fine read, and an interesting twist on Scandi-noir.

As is The Healer, the third novel by Finnish-born Antti Tuomainen, an advertising copywriter who made his fiction debut in 2007. The Healer won the Best Finnish Crime Novel of the Year award and was also shortlisted for last year's Glass Key Best Scandinavian Novel.

Set in Helsinki just before Christmas, it gets off to an atmospheric start, depicting a world finally overcome by the effects of climate change. Countries are sinking into the sea, there are riots and refugees and forest fires. Mexican drug cartels are firing missiles onto LA and San Diego. There are 13 wars or armed conflicts in the EU area alone and, worldwide, several pandemic warnings. Helsinki has not escaped, and those inhabitants who survive are fleeing to the far north in search of better conditions.

Tapani Lehtinen, a poet who has written three volumes of poetry, none of which has sold terribly well, is searching for his wife, Johanna, a newspaper journalist. The plot revolves around his search for clues as to her disappearance and around a serial killer known as The Healer. Its sparse prose style suits the dark, treacherous, rain-soaked environment of this dystopian vision of Helsinki. Tapani learns more about his wife's past than he could ever have suspected, and there's a neat twist right at the end, but none of the characters lingers particularly strongly in the memory.