The scene where Phyllis visits Walter shortly after her husband’s “death” doesn’t measure up to the rest of the movie.

 

It didn’t really make sense for Phyllis to visit Walter’s place so soon after the assassination. One would expect Walter to have exercised more caution and have planned for the possibility of Phyllis being under surveillance by the insurance company. A visit of this nature could have exposed the entire scheme.

 

It also did not make sense for Phyllis not to leave Walter’s door upon realizing Barton Keyes (the insurance investigator) was inside the apartment. Though her curiosity is justified, Phyllis is smart enough to avoid the risk of incriminating herself (and Walter) so easily. One could think of a whole host of justifications for why she would find it tempting to stay behind the door and listen in to the conversation, but nothing at the end justifies the risk of being found outside the door if Keyes were to abruptly open the door, as he later did.