15th century Europe - To foster good relations with its southern territories, the Holy Roman Empire has been sending one of its princes on yearly visits to the Kingdom of Italy.
Tomas is the son of a powerful Sienese family who have the privilege of hosting the royal visits. He's been spending his summers with prince Emil at a remote family estate in Civita. But Emil is an ostentatious, spoiled brat, and Tomas couldn't care less for such "honor." The only thing that makes the whole situation bearable is another boy in prince's retinue. Matthias is everything Emil is not: kind, easy going, and makes for good company; nicknamed "St. Matthias" for his God given ability to ease the effects of prince's grating personality.
Having to play nice with royalty is a pain, but Tomas' true worry is a private one - he's unfulfilled in his romantic life. Relationships seem so complicated. Pessimistic about anything long term, he's equally unenthusiastic about the casual life of a bachelor. But... what else is there?
Contemplation leads him stumbling into unexpected feelings for Matthias, his childhood friend. Consumed by this newly discovered attraction, and eager to forget his woes, Tomas dreams of a fun, uncomplicated summer romance.
But what awaits him is anything but simple. The young men who return to Italy the following summer are not the Matthias and Emil that Tomas once knew. Both have changed in unexpected ways, and more importantly, both are hiding something. Tomas soon finds himself drawn into a mystery spanning two years and three hearts - one of which is his own.