I would like to hear other reader's interpretations of the short story "Powers" by Alice Munro, which is the final story in "Runaway". The story left me with nagging questions. Did Ollie take Tessa to the mental hospital? How can the fact that Tessa told Nancy that she saw Ollie's dead body be explained? I assume that Ollie was lying to Nancy when he told her that Tessa had died of leukemia. What do you think?
I think that we don't know what the truth is. Even Tessa with her infrequent clairvoyance couldn't tell us that. I, like you, felt that Ollie was probably lying (he was at one point a writer) and that Tessa's memory is swiss cheese from the treatments she was given, so he can't be sure that she saw Ollie's body. This all assumes that we can trust Nancy's version of the truth as a narrator, which I think we can.
Both Nancy and Ollie have a connection to something beyond themselves. We hear Nancy speak about it first, in her diary and Ollie speak about when he comments on his relationship to Nancy. The keystone in their compulsion to that "something unusual" is Tessa. The way that they relate to her and her powers is probably what some might call the point of the story, if there is one.
The story is that Nancy tries to retrieve a part of her past, a transitory one that saw Tessa in several but none central to her life. The final fantasy, as she falls asleep and her dead husband leads her away, is what happened to her in life and kept her from the more unusal aspects of an existence like what Tessa and Ollie had. Ollie probably lied, but we don't know for sure. Tessa and Ollie diverged from one another, somehow, and Nancy, years later, only can tell a murky version of events.
Clearly Ollie was lying about Tessa's having leukemia and dying from it -- when he tells Nancy, in Vancover in the early 70s, he says it happened during the Korean War (early 50s), yet Nancy saw Tessa in 1968. So it's not a stretch to believe that he had her committed -- in the final section (Nancy's dream or fantasy or vision), we see Tessa embracing Ollie and hearing the crackle of the commitment papers in his jacket pocket. Even if we think that Nancy is having a dream rather than a vision, the fact remains that she knew both of them well enough for her dream to present them behaving plausibly; Ollie has always been a charmer, a user, a manipulator, so it's not hard to imagine him finding a way to dump Tessa after he could no longer use her -- or, more charitably, after he was worn out by their hand-to-mouth existence and was unable to take care of her.
About Tessa's seeing Ollie's dead body: When we hear from Tessa in 1968, she has clearly been somewhat disoriented by shock treatment and who knows what else -- by meds, by a possible breakdown in the years before Olllie had her committed, by some deterioration from years of living among mentally ill people. So it's safe to say that her memories (Ollie in the black cloak during their performaces) have fused with an enormous amount of anger and pain (he simply abandoned her), and in her mind he's dead -- his death is the fulfilment of the murderous anger she must have felt plus the only logical explanation for why he wouldn't have come back for her.