Outside, a doughty blackbird announces the start of a new day. Tilda sits up, fired with a determination to look for reason. For sense. For explanations. She believes the answers to the questions she has not yet properly formed lie with the lake, its history and its people. And luck, or something like it, has thrown in her path the perfect person to help her discover its past.

‘Come on,’ she nudges Thistle. ‘That feeble glimmer in the sky out there is what passes for sunrise in these parts. Best time of day for a run, so if you’re coming with me, shake a leg.’

Outside the wind has vanished with the night, and been quickly replaced by a light frost. Tilda pulls on her warmer running fleece and a thermal scarf to keep the icy air off her throat. She clips the pink collar and lead onto Thistle and they set off at a gentle pace. The dog looks sound and eager, and the pair are soon covering the hoary ground with ease. The wintry landscape begins to sparkle as the sun rises, so that the lake and its surrounding fields are rendered postcard pretty. Tilda takes the shortest route, and watches her new running companion closely for any signs of lameness or fatigue. She is impressed at the way the dog is able to lope along beside her, not once getting in her way or pulling on the lead. As they near the little wooden bird blind, she sees a figure emerging from it and recognizes Professor Williams at once. She waves to him, slowing to a halt, and waits on the path. Despite his years, the professor moves with strong strides, waving back, his binoculars around his neck, walking stick digging firmly into the ground with each confident step.

‘Good morning,’ Tilda calls to him. ‘You’re up early.’

‘Ah, dawn in winter is an excellent time for bird-watching,’ he tells her. ‘The migratory water fowl have either departed or arrived, and all have settled into their new habitats. Even so, the shy newcomers like to be up early to feed so as to avoid their more boisterous competitors.’ He indicates the dog. ‘I see you have a new friend.’

‘This is Thistle. She’s … been unwell. This is her first time out for a while.’

Professor Williams touches the brim of his tweed hat. ‘I’m delighted to make your acquaintance,’ he says to the dog, who wags her tail politely by way of reply.

‘I’m glad I found you,’ Tilda says, seizing the moment. ‘I … I want to ask you more about the lake. About its history. I was wondering … if you could spare the time…’

‘My dear girl, nothing would make me happier. May I suggest tea? I have a fire laid in the hearth at home. Your courser will look very fine in front of it.’

‘My what?’ Tilda asks, falling into step beside him.