Thursday's Child — Sandra Brown

Oh, why had she let Ann talk her into this masquerade, Allison thought wildly as her twin's fiance Davis embraced his "bride-to-be." Even two days seemed forever to the shy, serious scientist pretending to be the graceful, charming, sexy sister--and making a mess of it! Then there was Spencer Raft. The dashing man of mystery was Davis's best friend and undeniably attracted to "Ann," and couldn't understand why she responded to him as if no other man had ever touched her. When at last the charade was over Allison retreated to her lab, safe from the spell of the devastating stranger --until Spencer offered her his special help in an unusual experiment in love...

Hero: Spencer Raft
Heroine: Allison Leamon