Fortune's Lady

English supporters of the French Revolution threaten to overthrow their native monarchy in 1792 in this romance by the author of Sweet Treason. After her father is executed for subversion, outcast Cassandra Merlin is coerced into working as a government spy in order to woo a would-be assassin. She falls in love with another informant, Philip Riordan, a member of Parliament reputed to be a drinker and philanderer. They marry to satisfy a wager (Cass wins Philip's hand in a card game), but neither can admit to entertaining genuine ardor for the other. Their mutual distrust is fueled by Philip's ``friend'' and mentor, a compulsive liar, but the lovers' willingness to believe falsehoods from others who wish to keep them apart is predictable, a hackneyed genre device. A low point is Cass's rapid intellectual growth following her purchase of eyeglasses, although an action-packed sequence near the end offers some surprises. (Oct.)