The wedding of Lord Semine and Agnes hits a snag: the ceremonial sword, a gift from Lord Semine, vanishes! Your mission in *Kingdom Come: Deliverance 2* is to find it. Here's how.
Finding Lord Semine’s Sword
Radovan reveals the missing sword, mentioning a suspicious man in yellow he saw earlier. Your search begins with finding anyone in yellow clothing. Questioning these individuals leads to a clue: someone in yellow was seen heading upstairs in the stable.
Investigate the stable's upper level to find Hans, a man in yellow, attempting a romantic encounter. While not the thief, Hans witnessed Svatya, the bailiff's son (and the bride's brother!), taking the sword. Hans, however, didn't follow Svatya.

Confronting Svatya
Find Svatya near the musicians playing for the wedding guests. He's easily spotted by the stables, holding a sword. Svatya confesses to the theft, explaining his motive: to embarrass Old Semine by making him appear senile. He impulsively tossed the sword into a nearby pond.
Retrieving the Sword
Locate the pond. If you danced with Myshka, she'll have taken you there. Otherwise, find the pond behind Radovan's location (a door in the fence leads to it).

Retrieve the sword from the pond. Return to Radovan. You can choose to reveal Svatya's actions or simply focus on the sword's recovery. Once you return the sword, the wedding ceremony commences. Complete any time-sensitive tasks before speaking to Radovan, then celebrate the newlyweds and proceed to the next main quest.