CAMBRIDGE — There is such a thing as subtraction by addition. Take Katori Hall’s “The Mountaintop,’’ a feverishly imagined depiction of the final night in the life of the Rev. Martin Luther King Jr.

There are flashes of brilliance, but on balance this erratic two-hander feels like the work of a talented young writer who’s throwing a lot of things against the wall to see what sticks. Little does.