Ivan Puhov (Abdulov) is in love with a very kind and friendly girl, Alyona (Yakovleva). Alyona works as a witch in a research institution that researches magic called NUINU (Scientific Universal Institute of Extraordinary Services, a NIICHAVO subsidiary in Kitezhgrad; for NIICHAVO see Monday Begins on Saturday). The couple are about to get married when Alyona's jealous and scheming co-worker, Sataneev (Gaft), tricks Alyona's boss, Kira Shemahanskaya (Vasilyeva), the institute director, into putting a spell on Alyona. The spell makes Alyona undergo a severe personality change, become unable to control her actions, and forget about Ivan. Alena's colleagues, Viktor and Foma, notice a changes in her behavior and try to figure out a way to break the curse while simultaneously protecting the institution's latest research development, a magic wand.
The film was initially written by brothers Boris and Arkady Strugatsky as adaptation of their 1965 science fantasy novel Monday Begins on Saturday. But Bromberg turned down the script due to its serious tone and social commentary, and the Strugatskys had to rewrite their script as a light-hearted romantic comedy. As a result, the movie bore almost no resemblance to the book besides the setting and several characters' names. History later repeated itself with another film by SokurovDays of Eclipse (Dni zatmeniya).
