… or not…
Nope. 42 Court Street was not Nathaniel HOLMES’s house. I found the second best thing to walking around Plymouth with a copy of Davis’s book in 1883, namely looking at this map, an 1882 aerial view of Plymouth, with a copy of Davis’s book. Here’s a detail from that map, showing the courthouse and the next few buildings along Court Street; the small gap between buildings at the bottom is Howland Street:
As I read Davis, pp. 202–204, the building to the right of the square in the 1882 view stands on the lot granted in 1709 to Francis CURTIS; the house was built by Joseph BARTLETT. Next is the garden which is the lot granted about 1700 to Martha WAITE. Next is the house Davis describes as owned and occupied by Lewis G. BRADFORD, which in the 1874 map is labeled “Mrs ADAMS”.
Then comes Nathaniel HOLMES’s lot. I had to reread Davis’s paragraph about a dozen times and study the 1874 map before I understood that this lot and Nathaniel’s house were both divided in 1798 between different owners: in 1874 the southern half was Miss DAVIES’s and the northern half was Jane T. LANMAN’s, wife of Ellis T. LANMAN. You can see in this map it is to the south of where Howland Street meets Court street, not directly across from it.
After that is the house built by Ebenezer CURTIS, occupied in 1874 by John PERKINS, slightly north of directly across from Howland Street.
But, as you can see by comparison with the Bing map, it’s that last house that is present day 42 Court Street. The one to its left in the 1882 view, with the gable parallel to the street, is Nathaniel’s. And in the Bing aerial view (and the Google Street View) it is, unfortunately, gone, along with the garden lot and the BRADFORD house, all replaced by the modern extension of the BARTLETT house. Historical imagery in Google Earth shows the latter was built sometime before 1995.