Why did Bran Stark say 'chaos is a ladder' to Littlefinger and what does it mean?

Bran's response to Littlefinger during Monday night's episode of Game of Thrones holds more significance than you might think

There was much to love about last night's Game of Thrones: a long-awaited reunion between off-screen best mates Sansa (Sophie Turner) and Ayra (Maisie Williams), some killer pyrotechnics from Drogon, plus some long-awaited screen time from our favourite anti-hero, Bronn.

But before the final battle climax, which could have killed Nikolaj Coster-Waldau's Jaime Lannister (though if we've learned anything from the show it's that dead doesn't always mean dead) - we witnessed Bran / Three-Eyed Raven / Mr Mood Killer talking to Littlefinger at Winterfell.

One otherwise slow scene led to a brief exchange which carries more weight when you unpack what was said:

'I imagine you've seen things most men wouldn't believe' says Ser Petyr Baelish to Brandon, 'to go through all of that and make your way home again only to find such chaos in the world, I can hardly imagine.'

'Chaos is a ladder', Bran replies.

Littlefinger's shocked look when Bran says this is explained by the fact that 'chaos is ladder' is something Littlefinger himself has said before. This was way back in season 3, episode 6, when Littlefinger was still at King's Landing serving Joffrey, and Bran was hundreds of miles north on his way to The Wall.

Littlefinger: 'The realm. Do you know what the realm is? It's the thousand blades of Aegon's enemies, a story we agree to tell each other over and over, until we forget that it's a lie.'

Lord Varys: 'But what do we have left, once we abandon the lie? Chaos? A gaping pit waiting to swallow us all.'

Littlefinger: 'Chaos isn't a pit. Chaos is a ladder. Many who try to climb it fail and never get to try again. The fall breaks them. And some, are given a chance to climb. They refuse, they cling to the realm or the gods or love. Illusions. Only the ladder is real. The climb is all there is.'

Since he's had no contact with either Varys or Littlefinger since this conversation, he could only have seen it in a vision. The exchange doesn't cast Littlefinger in a flattering light, showing both his willingness to switch sides and grab power from the people he serves when things collapse. By repeating his line back to him, Bran is showing a deep mistrust of Littlefinger, and perhaps even a premonition of a future betrayal if the delicate balance of power tips away from the Starks.

Bran might not be the most dynamic Game of Thrones character, particularly if you prefer your GOT with - in the words of Elvis Presley - a little less conversation a little more action, but he could be the one who eventually saves his family from a serious betrayal.