Florentius insists that my wife has been kidnapped

I have almost completed my unique weapons hunt and I need the Dawnguard Rune Axe, I should do the last "Lost Relic" quest but Florentius keeps giving me a quest where I'm supposed to save my wife from a kidnapping. My wife is Lydia and she's my companion too, she's right behind me as I speak to Florentius and instantly disappears if I accept the quest. This is utterly ridiculous and I don't want to do this quest, I tried loading a save/exiting the Dawnguard fortress but he keeps saying the same thing, should I wait some in-game days to trigger the Lost Relic quest or what?