In the film's last galling twist, it's revealed that Harris is actually Smith's wife. This is all revealed in the most sentimental way possible, with Smith visiting Harris at her home and viewing a home video of her with his own daughter and… I'm not really sure… making the connection himself? In the world of the movie, his time in her grief-counseling group is a courtship ritual of sorts, or a way to coax him out of his amnesia.
Does the film end with Smith finding out that his "friends" at the ad company have been mentally sabotaging him? Nope, of course not. That would make too much sense. Instead, the film's final image shows Smith going for a chipper stroll in Central Park with Harris. He looks back over a bridge and again sees "Time," "Love," and "Death" smiling down at him, and then he looks away for a moment and they disappear, which suggests… I don't even know. That characters we know are actors were actually angels all along? That Smith is now seeing illusions thanks to his co-workers' plan? That the screenwriter had no idea how to end the movie so he just went for something vaguely uplifting?