While investigating Jon Arryn's death, Eddard Stark comes to learn that Jon and Stannis regularly visited Tobho Mott's weaponsmith to check up on a young boy, Gendry, Robert Baratheon's bastard son.

It is not clear to me how Gendry ended up working there, especially how his identity was initially discovered and why someone (still unidentified?) paid a high price for his internship at the smith.