What an FU ending...

It was added by the producers. The prologue, epilogue, narration and all the black & white flash forward scenes were done after the original director was fired from the movie. His original cut of the film (which was called "Army".) ends with Harrison finding out that Eva fused with his mother after getting her out of the lab but the original scene had Denise Wallace's actual voice rather than Elke Sommer's voice that was dubbed over the character in the released version.