You check the door of the lighthouse. Unlocked. You go inside. The building has a spiral staircase leading to the top of it and a pantry is built into it. Loads of preserves, mainly hard boiled crabs, they can stay good for years that way. No one seems to be here. From the top of the lighthouse you can see the smoke from the weapons lab. It must be a huge fire, what the hell?
Meanwhile people are dieing all over the island. But they don't stay dead. They rise as flesh eaters to devours the flesh of any living tissue. They eat all the crabs, the people, who then rise as partially eaten. When nothing is left to kill and eat they start wandering over to your side. One fearful day they enter the lighthouse forty five strong. You are asleep and they fall on you biting. You fight the first wave off, but the next three waves get you. You die die die.
The End