Batman is unique among the superhero community because-when all is said and done-he's just a normal guy in a suit. The physical and mental ramifications of this are staggering and are almost never addressed in Batman's stories.
But not here. In "I Am The Night," we see Bruce at his worst. He's realized how futile his efforts seem-1 man fighting against the legions of evil in the world- and wonders if it's worth it to keep going. And, on top of all his doubts, tragedy strikes. Jim Gordon, one of the few people Batman could consider friends, is shot in the line of duty (in a situation that Batman could have prevented).
The guilt eats away at Bruce (especially when he realizes that Jim Gordon is the same age his father would have been). So, he quits. Tosses the mask down into the Cave's depths and says goodbye to crime fighting before someone else in his close circle is hurt by his lack of actions.
Thanks to the combined efforts of Robin, Alfred, Leslie and Barbara, Batman realizes that he IS needed, and that the city would fall apart without him. He gets back in costume and comes through for his friend Jim when help is needed the most. And, as an added bonus, Batman learns that sometimes he CAN make an impact and improve lives.
Truly an excellent episode, and one of the greatest.