Once Upon A Time Season 4 will premiere on ABC tonight, Sept 28 at 8/7c. According to OUAT showrunners, Frozen's Elsa will be joined by her sister Anna (Elizabeth Lail) and Kristoff (Scott Michael Foster). Other characters will include Prince Hans (Tyler Jacob Moore) and Pabbie the Troll King (John Rhys-Davies). Sadly, the affable snowman Olaf will not be included in the fourth season storyline. 

In the new season, we will see a major power struggle between Storybrooke's Evil Queen (Lana Parrilla) and Frozen's Queen Elsa (Georgina Haig). The information was revealed in the recent extended trailer that was released by ABC network.

"I'm the queen," Elsa insists. Afterwards, the Evil Queen tells her confidante, the Mirror, "She [Elsa] needs to be removed."

OUAT Season 4 Episode 1 titled "A Tale of Two Sisters", the official synopsis says:

"A scared and confused Elsa from Arendelle finds herself in Storybrooke and creates a powerful snow monster for protection, Regina wonders if her relationship with Robin Hood has been completely quashed now that Marian's back in the picture, and in Arendelle of the past, Elsa's sister Anna wants to complete their parent's fateful journey and discover if their quest may have held the secret to containing Elsa's out of control ice powers." 

Based on the OUAT trailer that was released by ABC, Elsa passes through the town's landmark hangouts, leaving her chilly mark wherever she goes. None of Storybrooke's citizens recognize the new faces from Disney's Frozen. However, they do not seem particularly happy about seeing Elsa - with Snow White drawing her iconic bow and arrow at the perceived menace.

Last month, Once Upon a Time creator Adam Horrowitz explained that the reason for this confusion is because none of Frozen's characters show up in Henry's book. Also, the OUAT plot takes place a year before Frozen was released to theaters. So, Elsa remains a very mysterious figure to everyone at Storybrooke.

Back in July, ABC featured two sneak peak footages at the San Diego Comic-Con. One of those clips showed Anna and Elsa visiting the graves of their parents. Elsa apparently has a surprise for her sister, who is going to be wed to someone.

Meanwhile, Rumplestiltskin (Robert Carlyle) and Belle (Emillie de Ravin) prepare for their long-anticipated wedding. Snow White (Ginnifer Goodwin) and Prince Charming (Josh Dallas) are raising their second child - son and heir Prince Neil.

Once Upon A Time Season 4 is premiering Sunday, Sept. 28 at 8/7c on ABC. Fans can watch the show live stream at abc.go.com (free for cable subscribers), if you cannot watch it on TV, you can visit ABC official site next week and watch the entire episode for free.   

Season 4 Extended Trailer - Once Upon a Time