Sotah 5:1 says:
Just as the water checks her [the woman], so does the water check him [the man]
The rest of the discussion there is about how the physical consequences that happen to her also happen to the man she committed adultery with. This makes sense, but made me wonder what happens in a different case:
Suppose the husband warned his wife not to be secluded with Reuven. She is then secluded with him (and there are witnesses), but they didn't do anything ilicit. This would mean that she is required to drink (barring other circumstances that prevent her), and she won't be punished. However, what if she had meanwhile committed adultery with Shimon?
If the consequences of drinking the sotah-water fell only on her, I might think that her having committed adultery, even if it wasn't with the man she was warned about, could lead to punishment. But maybe she and Reuven are a package deal; she didn't have relations with Reuven, and since her husband didn't warn her about Shimon, they get away with it even though she knows adultery is a transgression. Is that correct? Or does Shimon mysteriously develop abdominal difficulties soon after this happens? Or do we understand that God will punish both the woman and Shimon in some other way but not through the sotah-water?