Strannye veshchi tvori︠a︡tsi︠a︡ v Novo-Araratskom monastyre. Poslushnikam stala i︠a︡vli︠a︡tʹsi︠a︡ tenʹ svi︠a︡togo Vasiliska, zloveshchiĭ Chernyĭ monakh pugaet i dazhe ubivaet li︠u︡deĭ. Bratii︠a︡ obratilasʹ za pomoshchʹi︠u︡ k ott︠s︡u Mitrofanii︠u︡, i tot otpravil v monastyrʹ bezbozhnika-Aleshku. Sovsem skoro ot nego stali postupatʹ strannye pisʹma, a potom on i vovse ugodil v psikhiatricheskui︠u︡ lechebnit︠s︡u. Vskore na ostrov otpravilsi︠a︡ polkovnik Lagranzh, chtoby pomochʹ Aleshke. No i on pogibaet pri strannykh obstoi︠a︡telʹstvakh. I togda v delo vmeshivaetsi︠a︡ neugomonnai︠a︡ monakhini︠a︡ Pelagii︠a︡, obladai︠u︡shchai︠a︡ nezauri︠a︡dnymi sposobnosti︠a︡mi k sysku. Strange things are happening at the New Ararat Monastery. The shadow of Saint Basilisk began to appear to the novices; the ominous Black Monk frightens and even kills people. The brethren turned to Father Mitrofaniy for help, and he sent the atheist Alyosha to the monastery. Very soon strange letters began to arrive from him, and then he ended up in a psychiatric hospital. Soon Colonel Lagrange went to the island to help Alyoshka. But he also dies under strange circumstances. And then the restless nun Pelagia, who has extraordinary detective abilities, intervenes in the case.