Splendour, Rear View.

The bridge above the deck (surrounded by Isenglass enclosure) is where Dennis waited out the argument Natalie Wood and Robert Wagner were involved in on the rear deck the night of Natalie's death. Wagner must have known Dennis was on the deck as the music was playing from the bridge. But Dennis wasn't "watching" so Wagner did not see him.  The middle doors open to the master stateroom where the loud arguing started.