Isn't kind of impressive how everyone in Daniel Deronda seems to either have a big secret or has to keep someone else's secret? The whole novel is filled with this vibe of "I know something you don't know." Probably the biggest secret is Daniel's true identity, which Sir Hugo keeps from Daniel for decades. Still, there are lots of other really interesting secrets at work. Maybe the biggest mess of secrets is the whole Lydia-Gwendolen-Grandcourt-Lush affair. Lydia is Grandcourt's big secret – he has kids with her but never married her. Lydia and Gwendolen meet secretly, and Gwendolen keeps her knowledge a secret. Lush arranged for the meeting, but Gwendolen doesn't know it. And then Gwendolen tries her best to keep her knowledge of Lydia's existence away from Grandcourt. Phew! Secrets are exhausting.
Gwendolen is made powerless by Grandcourt's secrets.
Gwendolen is better off knowing about Grandcourt's secret mistress.