Game of Thrones - Season 7, Episode 3 Synopsis
 

Episode 7 - 3
Title: "The Queen's Justice"
Directed by Mark Mylod
Written by David Benioff & D. B. Weiss
Original Air Date - July 30, 2017

Jon arrives at Dragonstone where Daenerys demands his fealty. He refuses and instead attempts to recruit her help in fighting the Army of the Dead. Following Tyrion's advice, Daenerys grants Jon access to the island's dragonglass. Melisandre avoids Jon and departs for Volantis. Bran, with Meera, returns to Winterfell and reveals his newfound-role as the Three-Eyed Raven to Sansa. In King's Landing, Euron presents Ellaria and Tyene as a gift for Cersei, who promises marriage after the war is won. She also awards him co-control of her military alongside Jaime. Cersei administers the same poison to Tyene that killed Myrcella, forcing Ellaria to watch her daughter's impending death and remain imprisoned with the body. In Oldtown, a healed Jorah leaves to find Daenerys. Ebrose praises Samwell ability to save Jorah but as punishment for his disobedience makes him copy old texts. Grey Worm and the Unsullied attack Casterly Rock, only to find that Jaime has led the bulk of the Lannister forces in an attack on Highgarden, while Euron's fleet ambushes and destroys the Unsullied's ships. The Lannister forces quickly overwhelm Olenna Tyrell's army. Jaime offers Olenna a quick and painless death by poison. After drinking it, she admits to poisoning Joffrey.

Source: https://en.wikipedia.org/wiki/Game_of_Thrones_(season_7)