In a brief exterior camera shot outside the house, Stella is seen looking out into the stormy night through a ground-floor window. The window she looks through contains only two window panes - an upper and a lower. When the scene shifts indoors, the same window suddenly is divided into four panes.
Nurse Little's attacker, briefly visible in the opening scene, has a markedly different physical build from the character revealed as the killer at the end, though they are supposed to be the same person. It is clearly two different actors.
At 17:44 when the housekeeper counts the seconds between the lightning strike and thunder clap, she remarks that the strike was 3 miles away because she counted 3 seconds. She explains that each second is one mile. Actually, every five seconds is roughly a mile. So 3 seconds would be roughly 3/5 of a mile or, since sound travels about about 1130 feet per second in air, then the lightning strike was around 3390 feet away.
Gus the cat ends up in the cellar to take care of a mouse seen by Stella. Later, Gus escapes through the open window, out into the storm and pouring rain. Later, he is seen outside an upstairs window, presumably soaking wet, and is bought inside the house. Just a few minutes later, Gus lays on Baker's bed, dry as a bone.