I found these renderings of an elegant French style manoir in a 1911 issue of Architectural Record.  The caption reads ‘Cottage at Bar Harbor, John Russell Pope, Architect’. There is no evidence that this house was ever been built, and I’m curious to know more.  
My best guess is that it was designed by Pope for his frequent Washington clients the Edward B. McLeans, she the Hope Diamond wearing mining heiress Evalyn Walsh.  They had bought Briarcliffe, a large old fashioned shingle style cottage at Bar Harbor in 1910, and the following year, the New York Times reported that they were remodeling.  Perhaps they had first contemplated tearing down Briarcliffe and changed their minds? 

In the end, they wound up adding a bowling alley wing, a ballroom with murals of the Bay of Naples, a third floor nursery suite above, and a wing for Mrs. McLean’s mother, Mrs. Thomas Walsh.  The resulting hodgepodge of turreted and shingled wings was held together by a new classical courtyard.   
Here is the courtyard, after the residence was abandoned by the McLeans, with dancers posing amongst the statuary.  The photograph comes from a 1948 issue of Life magazine, featuring dancers among the ruined estates left by the Bar Harbor fire of 1947.
As an aside, Briarcliffe was originally designed by William Ralph Emerson for J. Montgomery Sears, owner of America’s Cup challenger Puritan. Between the Sears occupancy and the McLean purchase, the cottage was rented by the John D. Rockefellers, Jr., and was the birthplace of their son Nelson.  And with that, I’ve wandered far from the original question of the identity of the mystery house.

(Please note the poor quality of the second scan from Architectural Record via Google Books.  This poor quality is something we can expect more of as libraries continue to purge books, and the people who scan can’t even be bothered to de-screen when they scan halftones.  Are you with me, Blue?  I think that a lot of important visual information will be lost.  We are soooo screwed.)