Mirage (1965) on Netflix

An accountant suddenly suffers from amnesia. This appears related to the suicide of his boss. Now some violent thugs are out to get him. They work for a shadowy figure known simply as The Major.

Walking down twenty-seven flights of stairs after the power goes out in the New York City office building he is in, David Stillwell emerges outside on the ground level to find that a man he didn't know either jumped or was pushed out a window to his death. That man was Charles Calvin, the head of Unidyne, a humanitarian organization that works toward world peace. David notices other unusual goings-on. What he considers his normal routine that others he knows should recognize, don't. People that he doesn't know seem to know him, such as the beautiful young woman with who he walked down the stairs but who ran off when they got to the bottom. And things that he thought he saw or thought he knew end up not being the case, such as the multiple sub-basement levels he thought were in that office building which don't seem to exist in the clear light of day. When he finally thinks about it, he believes he has some form of amnesia. As an example, he knows that he works as a cost accountant, but he has no idea what a cost accountant is or does. He soon learns that some people are following him and are after something that he has, he not knowing what it is, and that they will shoot to kill if they don't get it. Conversely, the young woman, who he learns is named Shela and was once a love of his, is trying to convince him to cooperate with the people after him if only to save his life. Every direction David turns for official assistance, he comes up not trusting anyone, with the exception of a novice private detective he hires named Ted Caselle. Shela and the people after David all refer to "the major" as the person at the top who wants what David has. David may have to look deep into his troubled psyche to come out of his amnesia to learn who the major is, what he wants, whether David is willing to give it up if he indeed does have it, and that the death of Charles Calvin had some part to play. But David may be dead before he can even make an informed decision to cooperate or not.

—Huggo

After an office party, David Stillwell discovers that he has no memory of certain people, people who should be familiar to him, or of anything about his life from more than two years previously. Then he discovers that the same night his boss, the famous businessman and philanthropist Charles Calvin, committed suicide by jumping out of his office window. Now some violent thugs are out to get him. They work for a shadowy figure known simply as The Major.

—grantss

An accountant's memory suddenly becomes mixed up starting from the moment the building he is in has a power blackout. He is bewildered that he can't recall even simple particulars of his job and places he does remember don't exist. Believing he has some type of amnesia, he tries to backtrack what happened before the blackout. Aided by a rookie detective and confused by an old girl friend, he tries to make sense of inconsistent facts while people around him are being murdered.

—Russell West

David Stillwell makes his way down several flights of stairs in the dark after the lights suddenly go out in his office building. He is accompanied by an attractive woman. Thanks to his flashlight, he can see her, but she can't see him. Still, she assumes she knows him by his voice and talks to him about someone named The Major, as if he should know who that is. The day becomes stranger when he gets outside the building and discovers that someone has apparently committed suicide by jumping out of a window. And then, when he gets to his apartment building, things get dangerous. Within the next two days, David will encounter a chubby gunman, a rude maintenance man with horn-rimmed glasses, an abrasive psychiatrist and an inexperienced but shrewd private detective. He'll also meet up again and again with the attractive woman. Most important, he'll encounter himself - because who he thinks he is and who he really is are two different things.

—J. Spurlin