Playwright Katori Hall grew up in Memphis, Tenn., hearing her mother and others remember the events surrounding the assassination of Dr. Martin Luther King, Jr. She came to speculate about the events, especially what was going through King’s head the night before his death as he decompressed from his rousing “I’ve been to the mountaintop” speech at the Mason Temple. Hall’s play, The Mountaintop, features two people in room 306 at the Lorraine Motel, where King spent his last night: One is a very human Dr. King; the other is a sassy maid who is considerably more than she first appears. Ensemble Theatre Cincinnati is offering the regional premiere of Hall’s powerful script.