It is difficult to know for certain what you consider the middle of The Graveyard Book by Neil Gaiman. However, one interesting adventure Bod faces in what seems to be the story's midpoint is Bod's attendance at the dance of the Macabray.
Bod is not supposed to leave the graveyard, but the other residents begins to talk mysteriously about an upcoming event in town, and their secretive messages to each other make mention of this occasion:
One and all will hear and stay
Come and dance the Macabray.
One day, Bod can smell the scent of flowers growing at the Egyptian Walk. Bod arrives to see a Mrs. Caraway, "the Lady Mayoress," collecting flowers with men that are carrying baskets. They cut flowers to fill all the baskets. Bod moves throughout the graveyard, but it seems abandoned, which frightens him. When Bod goes to town, people are milling about and every "Man, woman and child" is being given one of the flowers from the graveyard to wear. Most people take one, though no explanation is given other than "It's a local tradition."
Music is playing, though it's hard to tell from where it comes. Bod asks for a flower and learns that this tradition has come from years past, from "the Old Town...before the city grew around it." The people walk in time to the music or sway to the rhythm. Then the music stops and the clock strikes midnight. From the graveyard, its occupants—his friends and "family"—walk down the hill. Some people in the town square are frightened, but others don't seem to notice anything unusual. The ghosts dance with the people.
Liza Hempstock, the ghost of the young witch, takes Bod's hand and they dance, and Bod experiences great joy. The dance steps come to him easily...
...his feet moved as if they know the steps already, had known them forever.
The living and the dead dance. Liza tells Bod that the living don't remember the dance when it's over, but the ghosts do. The Lady on the Grey arrives, and the dance starts over, as those present say:
Now the Lady on the Grey
Leads us in the Macabray.
Bod sees Silas watching, but his guardian disappears into the shadows. Bod then joins in the last dance with the Lady on the Grey and they speak. When the dance is over, Bod feels suddenly very tired. He looks around and his friends and the Lady on the Grey have left. The townspeople sleepily make their way home.
The town square was covered with tiny white flowers. It looked as if there had been a wedding.
This chapter is entitled "The Danse Macabre," and I believe that Macabray is a form of the word "macabre" for "Macabray" is how the word "macabre" would sound if spelled the way it looks, but is it French and sounds like "ma-'kab" (as the "e" is silent). "Macabre" can refer to something relating to death, but also it is:
...suggestive of the allegorical dance of death.
The next day, no one will speak of the events of the night before. Bod gets frustrated and angry. Josiah Worthington says:
The dead and the living do not mingle, boy…If it happened that we danced the danse macabre with them, the dance of death, then we would not speak of it, and we certainly would not speak of it to the living.
So it would seem that the dance was, in fact, the dance of death. This was Bod's adventure in Chapter Five.