Glow-in-the-dark dragon on an arm

Mr Ansell kept the caretaker's cupboard under the stairs, and in it was a black lamp he'd borrowed from the chemistry store and never returned. Every Friday he took it down to the boiler room, where some boy had scratched a dragon into the lime wash decades before. Under that lamp it lit up green, coiled from the pipes to the door, its claws hooked round the stopcock as if it were guarding the heat. He said it got a little hungrier each winter, and he fed it nothing but a clean cloth and a few kind words.

Miss Crane, the secretary, wanted the wall painted over before the inspectors came. Ansell refused. Then one December the lamp's bulb blew the night before the Christmas concert, and the boilers went cold. He went down with a torch expecting the worst, and found the dragon had moved its long tail across the doorway, pressed tight against the frost, keeping the pipes from bursting. He swore afterwards it had winked at him.

So when you get home tonight, don't go rubbing that old scratch off your own wall. Check the bulb in the hall first. Right, lights back on, and somebody find me my tea.