This is a more comprehensive synopsis that I’ve written based on new sources that have been coming in, including more westeros.org commenters and @brokenrecord here on Tumblr.  It’s been confirmed that this is Arianne’s second chapter in TWOW, one of two Arianne chapters intended for ADWD that were pushed back due to space issues.

SPOILERS FOR THE WINDS OF WINTER

Princess Arianne has been dispatched by her father to meet with Lord Jon Connington and Prince Aegon, as Prince Doran was informed of their arrival in Westeros in Arianne’s previous chapter.  She is accompanied by a Dornish retinue that includes Elia Sand — the eldest of the younger four Sand Snakes, Oberyn Martell’s daughters by Ellaria Sand — and Daemon Sand, the Bastard of Godsgrace, who appeared in ASOS as Oberyn’s squire and was noted in AFFC to have been Arianne’s first lover.  Nymeria and Tyene have also left Dorne, with Princess Myrcella and 300 spears.  Arianne’s brother Trystane remains safe at the Water Gardens.

While en route to Griffin’s Roost, Arianne contemplates whether or not Quentyn ever reached Daenerys and married her.  She thinks about how Dany is but a young maiden, and thinks that Quentyn, who is unremarkable-looking and not very dashing, is unlikely to impress someone Dany’s age.  Still, Arianne thinks Dany will want Dorne enough to marry Quentyn; she wonders if she will have to call her brother ‘King Quentyn’, which she thinks sounds rather silly.  She’s shaken out of her reverie when she realizes her cousin Elia has been missing for a while, and goes to look for her. 

Elia is in a cave catching fish with her bare hands in a pool.  Arianne is furious with her for running off, and Elia gets a bit petulant because she doesn’t think that she did anything wrong.  Arianne makes her promise to behave, as she’s supposed to be pretending to be one of the Princess’s maidservants.  She shouts at Elia that the girl could have died in the cave, and ‘died’ echoes ominously three times against the walls.  Arianne confides in Elia that she often wishes Oberyn had been her father instead of Doran.  On the walls of the cave they find carvings left behind by the Children of the Forest.

The party is met by two Golden Company men, Young John Mudd and Chain.  They won’t tell Arianne much, but eventually she gets Chain to admit that Connington has left for Storm’s End.  Arianne thinks that’s preposterous, as she considers the various castles in Westeros and proclaims that Storm’s End would be the most difficult to capture. 

Despite their earlier talk, Elia continues to misbehave; Arianne catches her making out with a servant named Feathers who is twice her age.  Arianne yells at her and Elia protests that it was just kissing; Arianne reminisces privately about losing her virginity to Daemon at the same age.  The two women argue over who would be a more attractive hostage, and then Elia promises again to behave.

Golden Company spymaster Lysono Maar meets the party and begins to lead them.  Arianne does not care for him, and describes him as looking like a Targaryen.  Lysono and Arianne debate Aegon vs. Dany.  Lysono says that Aegon has Dornish blood, to which Arianne replies that so does Daenerys.  He then proclaims that Aegon is the Dragon, to which Arianne replies that Daenerys has three.  Along the way Arianne contemplates whether Connington is worthy of Dorne’s assistance; she believes he will need the Dornishmen to take King’s Landing.

Upon arrival at Griffin’s Roost, Arianne is informed by Haldon Halfmaester that Connington has not only already left for Storm’s End, but has successfully conquered it; the Tyrell armies are coming from King’s Landing now to try to take it back.  Arianne is stunned at Connington’s success.  Haldon tells her that Connington and Aegon want to meet her at Storm’s End, and Daemon begs her not to go into danger.  Arianne rebukes him, saying that she must be her father’s true heir and go to meet this ‘Dragon.’