Vigil (BBC) Rating:Lions can be fended off with a chair. A punch on the nose deters sharks. But never try to keep a polar bear at bay by belting it with a police truncheon. This will only antagonise it.Every citizen on the Arctic archipelago of Svalbard is required to carry a rifle, not a wooden stick, when venturing beyond the settlements, explained police chief Henrik Becken (Jeppe Beck Laursen) in Vigil.He presented visiting copper Kirsten Longacre (Rose Leslie) with a high-powered hunting rifle: ‘Keep it loaded and on your shoulder,’ he warned. ‘Polar bears move fast.’So far, the only predators we’ve seen in this snowbound action thriller are Russian special forces. But I’m willing to bet my last glacier mint that Kirsten and her boss Amy Silva (Suranne Jones) are fighting off packs of ravenous bears before the end of this six-parter.We haven’t reached that point yet, because Amy is still at home in Scotland. She’s not only Kirsten’s senior officer but her partner, too: the two women have a child together, which does rather complicate their work/life balance.Their relationship has been established over the previous two series, and reminding us of it took up too much of the opening episode. Kirsten Longacre (Rosie Leslie) and Amy Silva (Suranne Jones) are back on screens tonight in Vigil and Christopher Stevens’ verdict is in…For a story that opened with an attempted defection, as Chinese climate scientist Shen Jia (Naomi Yang) tried to flee Svalbard, and then a firefight, a murder investigation, a bomb attack on a university lab, another murder and the kidnapping of a government minister at gunpoint, this hour still managed to sag and drag in places.But the central premise is a strong one. Sir Richard Shirreff, a former deputy commander of Nato, warned in the Daily Mail earlier this month that Svalbard could easily become the flashpoint for a Third World War, and Vigil’s plot might have been lifted straight from his predictions.Russia maintains a mining base on the islands, 580 miles north of Norway, under a 1920 treaty. Lodes of rare minerals make this a far more desirable territory than it was a century ago, all the more so now that melting sea ice means it could serve as an Arctic naval base.If Putin stages a military provocation here, how will the West react? That’s up to Amy and Kirsten, who have to discover whether Russia is behind the killings — or if the denials of a handsome colonel from Moscow (Tornike Gogrichiani) can be trusted.The unspoilt landscape of Svalbard, with its luminous skies and frozen mountains, has an almost lunar beauty, and gives the drama a special appeal. Crime shows such as True Detective and The Killing began a tradition of staging murder investigations in unfamiliar settings with an ethereal atmosphere, but new backdrops are hard to find.It’s becoming a popular tourist destination too. Polar bears still outnumber humans, though. Keep that in mind before booking a skiing holiday.