Bang. Bang. Bang.

I hammer on the door and scan the windows. Suddenly the light inside goes out, plunging the porch into darkness. My heart leaps into my throat. Why would she turn it off? I blink as my sight adjusts to the pale moonlight. The wind is so loud Mormor can’t have heard me knock, that’s all. She must have turned off the light and gone to bed.

I peer through the dark window and see an oil lamp on the table, its flame dying. Mormor would never go to bed and leave a flame burning, even a low one. Something is wrong.

‘Mormor, it’s me, Martha!’

A shape inside the cabin darts past the window. My legs turn to water. I’m sure it was a man, bent low. Why is there a man in Mormor’s kitchen? There has to be an explanation. Think, Martha. Where is Gandalf? Why isn’t he barking? Maybe a burglar poisoned the dog. Or maybe Mormor went somewhere with him. Maybe she’s looking after a sick neighbour, and that’s what Olav was worrying about.

I grab my bag, the taste of vomit in my mouth. My hands shake as I scrabble for my phone. One bar. Even if I get through to Mum or Dad, what are they going to do?

My pulse quickens as a shadow races behind me. Get a grip, would you? It’s just a cloud passing in front of the moon. But what if Mormor is in trouble and needs me? I can’t stay out here. I sling my bag over my shoulder and gently nudge the door. It opens with a creak.

‘Mormor?’ My voice is barely a whisper. I reach to turn on the light, but I can’t find the switch. I turn on the torch of my phone and hold it out before me, then lick my lips and swallow. The sound that comes from my mouth is a frightened squeak. ‘I know there’s someone in here. I saw you from outside.’

I scan the kitchen to my right. The oil lamp gutters on the wooden table, its flame casting strange shadows about the room. The little dresser is there with its row of blue flowery crockery. The colourful rag rug is where it should be. Mormor’s books are all in place. The wooden chairs are tucked neatly under the table.

The kitchen smells strange – of boiled potatoes and vinegar. The tap drips with a rhythmic plop. A pan and dirty plates are stacked on the draining board. Mormor would never do that. What’s going on?

My fingers tighten on the strap of my rucksack as I enter the open-plan living room. Embers glow red in the cast-iron stove to my left. It looks sinister in the dark: a pot-bellied monster on stumpy legs. Above it is the painting Mum did of the island, the choppy waves of the sea glinting in the half-light. The blue and white checked sofa facing it is empty. I go to the back of the cabin. Three more rooms: Mormor’s bedroom, the spare room and the bathroom.