"For some time Bilbo sat and thought about this water-gate, and wondered if it could be used for the escape of his friends, and at last he had the desperate beginnings of a plan."
Opportunity;
"When he heard this Bilbo was all in a flutter, for he saw that luck was with him and he had a chance at once to try his desperate plan."
"Very soon the chief guard nodded his head, then he laid it on the table and fell fast asleep. The butler went on talking and laughing to himself for a while without seeming to notice, but soon his head too nodded to the table, and he fell asleep and snored beside his friend. Then in crept the hobbit. Very soon the chief guard had no keys..."