In "The Open Window," when does Framton explain his medical condition to Vera?

Framton Nuttel never says anything about his medical condition to Vera. Vera has to do most of the talking because Framton is silent and ill at ease with her. He does tell her aunt Mrs. Sappleton all about his condition when she arrives to take over as hostess from young Vera.

"The doctors agree in ordering me complete rest, an absence of mental excitement, and avoidance of anything in the nature of violent physical exercise," announced Framton, who laboured under the tolerably widespread delusion that total strangers and chance acquaintances are hungry for the least detail of one's ailments and infirmities, their cause and cure. "On the matter of diet they are not so much in agreement," he continued.

Before Mrs. Sappleton arrives, Vera just has time enough to find out Framton is a complete stranger in the region and knows virtually nothing about her family, and then to tell him her totally fallacious story about the three hunters who were sucked into the bog three years ago. If Vera knew about Framton's nervous condition, she likely would not have told him her ghost story at all.