Patricia Hagan, Love and Triumph (1991)

: Zoom

From the novel's blurb:

"All Russia was being consumed in the terrible flames of war as the centuries-old Czarist dynasty crumbled. A prisoner in the midst of chaos and destruction, beautiful Marilee Coltrane Mikhailonov feared for her life at the hands of bloodthirsty revolutionaries. But the dashing, blue-eyed counterspy, Cord Brandt, would allow no harm to come to his bewitching captive. Across a vast continent, Cord would pursue Marilee’s elusive heart as she set out to reclaim her lost heritage. And together they'd fulfill a remarkable destiny — triumphant at last in the rapturous glow of a magnificent love.

Editorial Notes

Lenin also features in this novel, but the text doesn't dwell on his time in Zurich.
The coffeehouse Wolfa, situated in Hagan's novel in the "Schulleslgasse," may be entirely fictional.