NoDictionaries   Text notes for  
... amoenos promittit, vel, si negavisset, necem intentat. ille, insita...

This represents fut. perf.indicative in o.r., "if he denies/(lit., "shall have denied") [committing adultery]." In so-called minatory conditions using the indicative, English idiom uses the present indicative in the protasis and the future in the apodosis, Latin the future perfect in the prodosis (with more precision according to so some pedants) and the future in the apodosis. English: "if you say this, you will be mistaken"; Latin: "si hoc dixeris, errabis." When such a conditional sentence is embedded in o. o., the future perfect becomes the perfect subjunctive after a man verb in a primary tense (although the two forms are identical except in the first pers. sing) and the pluperfect subjunctive after a main verb in a historic tense. So, I think, this accounts for the pluperfect subjunctive here. Nero said to Anicetus, "si negaveris te hoc facturum esse, morieris."