Crop Circles.

A man is trying to sell a piece of land with a crop circle on it. An FBI agent tries to arrest him for this, but he gets away. He find instead an alien tool, which a shape shifting alien steals back. He/she shows the agent the crop circles as a trade for keeping the land. A spaceship lands and the agent enters it. He finds a decaying alien, with an egg on it. He gets chased by another alien and kills it, only to have it regenerate and kill him. The agent is healed by an alien and knows they'll return!