It's a well known fact that the fairytale-based series will be having a crossover with Disney's hit movie "Frozen." During this season, Regina, the evil queen, and Elsa, the ice queen, will meet for the first time. Like all things in life, there can only be one alpha--but in this case, one queen--and the same goes for "Once Upon A Time's" Storybrooke.

Two weeks ago, ABC shared the extended trailer of season 4 and it's pretty obvious that Regina (Lana Parrilla) and Elsa (Georgina Haig) will butt heads. Around the 45-second mark, Elsa says, "I'm the Queen."

In the minute long trailer, you'll see Regina who is mending a broken heart, back to her old ways--scheming with her magic mirror. Queen Elsa's presence seems to disturb the evil Queen Regina who then tells her accomplice, the Magic Mirror (Giancarlo Esposito) that, "she needs to be removed."

"The two queens have so much things in common, including their back-stories of love and loss as well as their desire for power. Thus, the audience can expect an intense struggle for supremacy between the two queens," wrote Christian Today regarding the two powerful women.

We now know more about the season premiere as website Hypable shared the synopsis of the first episode, titled "A Tale of Two Sisters" that highlights the developments in the fourth season.

According to the synopsis, "a scared and confused Elsa from Arendelle finds herself in Storybrooke and creates a powerful snow monster for protection."

Queen elsa will be remembering, through flashbacks, her life in Arendelle, where, "Elsa's sister Anna wants to complete their parents' fateful journey and discover if their quest may have held the secret to containing Elsa's out of control ice powers."

Regina, on the other hand, has problems of her own surrounding her romance with Robin Hood, whose wife Marian has appeared.

ABC noted in its press release via Hypable that the town will prepare to defend themselves against Queen Elsa of Arendelle, a magical force that is described to be "too unpredictable even for Rumplestiltskin."

Expect to see other "Frozen" characters joining the series--such as Princess Anna (Elizabeth Lail) and her fiance Kristoff (Scott Michael Foster), to name a few.

Catch the fourth season of ABC's "Once Upon A Time" when it airs on Sept. 28, 8:00 pm. For chills and excitement, see the "Once Upon a Time" season 4 Extended Trailer below: