The 13th Floor: A Ghost Story, Paperback/Sid Fleischman

When Buddy Stebbins stumbles onto the thirteenth floor of a shabby old building, he finds himself suddenly transported aboard a leaking pirate ship in a howling storm--three hundred years in the pastCast adrift with Captain John Crack-stone, Buddy washes up in New England, where his plucky ancestor, Abigail, is caught up in the witchcraft mania. In an adventure filled with ghosts, witches, pirates, and razzle-dazzle treasure, Buddy might be able to save his wayward ancestors. But will he find his way back to the thirteenth floor--and home?