"Tosca" (1900) is the middle work in what one could justifiably dub the 'holy trinity' of opera masterpieces by Giacomo Puccini (1858-1924), the others "La Boheme" (1896) and "Madama Butterfly" (1904). Based on a play (1887) by the French author Victorien Sardou (1831-1908), "Tosca" is set in Rome, summer 1800 in three acts, each in an iconic, still-extant site of the city, in order Church of Sant'Andrea della Valle; Palazzo Farnese; and Castel Sant'Angelo (CS'A, uploaded photo).

One could call "Tosca" a love triangle deadly for all as Floria Tosca, an opera/concert singer, stabs Baron Scarpia, the lecherous chief of the Roman police who lusts after her. Subsequently Tosca goes atop the CS'A hoping for rescue and release of Mario Cavaradossi, her mutual love interest. However a 'mock execution' becomes all too real for Mario. Soon Scarpia's henchmen corner her atop the CS'A, from where Tosca, with absolutely no hope of escape, jumps to her death, before which she proclaims 'Scarpia, we'll meet before God!'

Cesare Angelotti is a prison escapee; Mario's friend; and Scarpia's primary target of pursuit who only appears and sings in Act I, but he's the whole reason for Tosca's and Mario's entanglements in Scarpia's clutches. Just as Tosca would to end the opera, Angelotti commits suicide when Scarpia's henchmen finally corner him. The event is not shown in the opera, only mentioned about by Spoletta, Scarpia's chief henchman, in Act II.

More Info: en.m.wikipedia.org