This is a summary, rather than a quote from the book.
Jon dreams of the direwolves, and realizes that one of the female wolves is dead. Then he hears a voice behind him, a silent shout or whisper, and he looks around, searching for a lean grey shape. He sees a sapling weirwood rapidly growing from the cliff side, and it has Bran's face, except it has three eyes. He wonders if his brother always had three eyes, and the weirwood tells him that it wasn't the case until the crow. John smells wolf, tree and boy, and warm earth, hard stone and death. Bran tells him that he likes it in the dark, and then the weirwood touches Jon to open his eye. Suddenly Jon slips into Ghost and sees things from his perspective.
Clearly Bran's powers have increased to the point where he is able to contact Jon Snow. The "lean grey shape" may be Summer, suggesting an instinctive understanding that the voice was Bran's, yet it could also be Grey Wind, the brother with whom Robb identifies most closely. The smells Jon scents, and Bran's words, correspond with Bran being in the Stark crypt. Finally, his pushing Jon into Ghost's skin is a remarkable feat.
What seems to be clear now in A Dance with Dragons was that a line given to Bran in the course of this dream must surely be foreshadowing: "... I like it in the dark. No one can see you, but you can see them." Of course, Bran is hiding in the crypts of Winterfell at that point, down in the dark, but in retrospect it seems to have been a hint of things to come.