What's Marias's novel Your FaceTomorrow (vol 1) about?

Yes, I'm still enjoying reading Javiar Marias's Your Face Tomorrow: Fever and Spear, though to be honest I don't (yet?) know what the novel is about. The first 150 pp or so consist of the narrator, Deza, meeting with his Oxford mentor, Peter, who asks him to attend a dinner party he's holding and to report to him all his observations about one of the guests, Tupra. We get a long chapter about the party and a long follow-up conversation between Deza and Peter (can't remember his last name); Peter retires for the night, and Deza, spurred by some comments from Peter, spends the rest of the night, till near dawn I think, doing research on the Spanish (Civil) War (he's a historian, although his academic posting seems to be a cover for some other line of work, probably espionage). He's pursuing a thread of an idea that Peter may have been involved in the post-war execution of Communist/leftists partisans, a series of mass executions obviously carried out by the victorious Franco though, oddly, or maybe not so oddly really, in alliance w/ Stalin. A few quick check of a few facts and topical references show me that Deza's research is based closely on the facts. All of this makes for good reading, on the surface, yet even this far into the novel I can't honestly say what it's about: If this is a spy novel (and there are some sly references to other spy novelists and to Ian Fleming) we have only hints and glimpses. We don't really know who's working for whom or what info either Deza or Peter want to elicit, or why. After all, this whole novel, to this point, may be about nothing more than a dinner party and the host's curiosity about the background of one of his guests (and his guest's date, whom we learn is his ex-wife now making a bid for a reconciliation). But probably not.