To me, Karen Black is one of the saving graces of B-movie cinema. Gorgeous yet cross-eyed, and gifted with an extremely complex personality, she can single-handedly make a film both enjoyable and endlessly watchable (for example, compare the lifeless 'Torn Curtain', with Paul Newman and Julie Andrews, with 'Family Plot', which starred Black with Bruce Dern--on paper, TC should have been much better than FP, but it simply isn't). Before watching this low-budget, Canadian-made suspenseful thriller on the horrific possibilities of astral projection, I loved watching her in films as diverse as 'Easy Rider', 'Five Easy Pieces', 'Nashville', 'Airport 1975', 'The Pyx' and 'Invaders from Mars', and here, she's the only name actor (other than wonderful cameos by the likes of Lois Maxwell, who starred as Miss Moneypenny in the Bond films).
Because it's so low-budget, it has to work on atmosphere. I wish Black had more screen-time--her co-star is a bizarre cross between Dudley Moore and Willem Dafoe, without much character or charisma, though he tries his best. The soundtrack is spotty--some of it really works well, in its delineation of various cultures, especially. Some of its themes seemed to be heavily influenced by Tangerine Dream's 'Le Parc' album, from that period. If you have patience with the flow, it's a particularly rewarding endeavor. The big reveal at the end is well-done, though it would have made more sense had the postcard been mailed. It just being left on the restaurant table, from who knows what location in the world, is most probably meaningless.