Tasked with writing a short story set in an isolated lighthouse, develop a tale that combines elements of mystery, suspense, and supernatural. Flesh out your main character, the lighthouse keeper, and aim to make them complex, facing personal struggle and battling internal demons. Additionally, unfold a plot which reveals a hypnotizing enigma linked directly to the lighthouse itself. Enhance your work with vivid descriptions to draw your reader into the chilling and eerie atmosphere of your setting. The sea, the storms, and the solitude should play significant roles as you weave your plot. Pay special attention to pacing and the resolution of your mystery.