November 2, 2014 (UK) / February 8, 2015 (US). IMDb Key Plot Points:
In Braavos, Arya continues her training at the House of Black and White, learning the "Game of Faces."
A high-strength repair wrap that hardens like steel. [S5E6] Episode #5.6
Jaime Lannister and Bronn attempt to rescue Myrcella but are intercepted by the Sand Snakes.
The episode reveals the origin of the rivalry between JJA and Karlov, dating back to 1994. November 2, 2014 (UK) / February 8, 2015 (US)
Below are guides for the most likely series matching that specific numbering:
Sansa Stark is forced to marry Ramsay Bolton, a controversial and dark turning point in her arc. 5. Shark Tank (Season 5, Episode 6) Original Air Date: October 25, 2013. IMDb Featured Pitches: The episode reveals the origin of the rivalry
Violet (Maggie Smith) reveals the truth about her past with Prince Kuragin to Isobel Crawley.