The Hallway under the Stairs

You decide to go back through the door exiting the kitchen. You pass the doorway and discover that you've entered a narrow hallway.

A few windows against the wall allow a small amount of sunlight to spill into the shadowy hall. Your eyes finally focus and you see that ahead lies a closed door and to your left is the way back out to the main room. Which way to go?

 

Ahead to the closed door?

or

Back out to the main room?

Or back into the kitchen?