How To End A Thriller

Sometimes, near the end of a thriller, the villain has the hero at gun point and could kill him but delays, giving the hero a chance to turn the tables. The classic example is Donovan Grant and James Bond in From Russia, With Love.

The conventions of this genre require that:

the hero's life is threatened;
nevertheless, he survives;
his survival is not too implausible.

At the end of Poul Anderson's Rogue Sword (New York, 1960), Gasparo, the villain, points a cocked crossbow at Lucas, the hero, and tells him to drop his sword, which Lucas does. So:

(i) Why does Gasparo not kill Lucas immediately?
(ii) How does Lucas survive?
(iii) Is his survival reasonably plausible?

(i) Gasparo does not shoot immediately because he wants to make Lucas hate him and die unshriven (a horrible inversion of Christian belief in damnation) so he starts to tell him how he will torture and kill Djansha, the heroine.

(ii) Djansha, who had been lying bound behind the standing Lucas,"...had cut her bonds with his sword while Gasparo's attention was diverted." (p. 279) She leaps up and throws the sword at Gasparo who shoots but misses...etc.

(iii) Verdict: Gasparo's motivation is horribly plausible; Djansha cutting her bonds with the sword less so.