The official synopsis of the opening episode of 'The Big Bang Theory' Season 9, which premieres on CBS on Sept. 21, has been revealed by a report in TV Line.

Quoting the report in TV Line, IB Times states that in 'The Big Bang Theory' Season 9 episode 1, viewers will find Sheldon Cooper confronting a mystery of the universe, which he is unable to solve. He is entangled into the mystery of "when a woman wants time apart to think, exactly how much time does that mean, and is there any way to hurry the process along?"

Meanwhile, in Las Vegas, Penny and Leonard get closer to walking down the aisle, but it still remains to be seen if Penny has been able to overcome Leonard's infidelity. If she has, will Leonard do anything to get her back over it?

Viewers will recall that 'The Big Bang Theory' Season 8 finale ended on a cliffhanger, as Amy breaks up with Sheldon, before the final moments of the episode revealed that he was planning to propose to her. Elsewhere, Leonard and Penny were seen driving to Las Vegas to tie the knot, but when he confessed that he kissed another woman during a research expedition to the North Sea, Penny become unsure about proceeding with their marriage plans.

In 'The Big Bang Theory' Season 9 opening episode, viewers will see Sheldon trying to disentangle the mystery behind how long Amy wants to be away from him, and how to make the separation lesser. On the other hand, Penny and Leonard will be seen in Las Vegas very close to marching down the aisle.

However, fans of the American sitcom created by Chuck Lorre and Bill Prady are eager to know if Leonard's infidelity will ruin his chances of marrying Amy. One report claims that the upcoming season will introduce the woman whom Leonard kissed while on the North Sea expedition.

The report in TV Line suggests that Melissa Tang will portray the character and she will appear in 'The Big Bang Theory' Season 9 espisode 2.