Luna, a cruise ship chambermaid, has to quit her job to attend to her sick brother. While doing so, she discovers that her mother has gone missing and her brother's condition is getting progressively worse. The siblings desperately sneak into an empty condo unit but soon discover that Penthouse 77 is not what it seems.

　　2020年，魏德被男友劈腿，加上新冠肺炎疫情爆发，他决定躲到外婆家并疗癒情伤。在进行断捨离好重新出发的同时，他意外发现满满一袋的情书，而且这些情书还是来自将近半个世纪前。撰写者是一名叫作荷西曼努尔的男子，当时是保守的1970年代，加上必须维护军人父亲的名誉，他只能私下透过书信对男友路易斯表达爱意。深受感动的魏德不禁回覆，未料一封回信竟从天花板落下……