In the middle of winter, with 17 hours of darkness, nearly 500 competitors head north of Inverness for one of the world's hardest mountain bike races - the Strathpuffer 24-hour marathon. This year Dougie Vipond has teamed up with mountaineer Mark Diggins to take on this toughest of challenges. For weeks, the track has been submerged under snow and now as the thaw sets in, it has been compacted down to ice. This promises to be one of the hardest Puffers yet. Also in this month's programme, Grant MacNicol cooks up some culinary magic to keep the bikers going through this long winter night, and we are joining Cameron McNeish on his monthly pilgrimage to the mountains.