Fans of The Big Bang Theory have been given a clue about the new season premiere storyline.

Answering fan questions about the season premiere, TVLine's Michael Ausiello said: "For those curious about Sheldon's whereabouts all summer, I can confirm that he did, in fact, get on that train (vs. just squatting in the station, as some have speculated)."

Ausiello added: "The bigger question you should be asking yourself is whether he ever stepped foot outside the train during his epic journey."

The new season premiere airs on US television on September 22.