In Kingdom Come: Deliverance 2, Lord Semine's wedding to Agnes faces a snag: his ceremonial sword has vanished. Your mission: recover it.
Radovan reveals the missing sword, a creation from the Hermit's Sword. He recalls seeing a man in yellow acting suspiciously. This leads you on a quest to locate individuals in yellow attire.
Questioning several yellow-clad individuals yields a clue: a man in yellow was seen heading upstairs in the stable. Investigating the stable's upper level reveals Hans, romantically involved with a woman. While wearing yellow, Hans isn't the culprit but witnessed the theft, implicating Svatya, the bailiff's son (and the bride's brother). Hans, however, didn't follow Svatya, leaving you to find him.
Locate Svatya near the musicians playing for the wedding guests. He's easily identified by his possession of the missing sword. Svatya confesses to stealing the sword to embarrass Old Semine, believing the act would highlight Old Semine's perceived senility. He carelessly tossed the sword into a nearby pond.

The pond's location is near Radovan; a gate behind him leads to its edge. The sword is visible in the water. Retrieve it.

Return the sword to Radovan. You can either reveal Svatya's involvement or downplay the incident. Once the sword is returned, and any time-sensitive pre-wedding tasks are completed, the wedding commences. Congratulate the couple and proceed to the next main quest.