Motifs in the James Bond film series the degree to which Bond girls are pivotal to propelling the plot forward varies from one film to the next. Five of the Bond girls are "bad" girls (or at least working for the villain) who turn "good" (or switch sides) usually due to Bond's influence. Bond has fallen in love with only Tracy di Vicenzo in "On Her Majesty's Secret Service" and Vesper Lynd in "Casino Royale", but both of them die at or near the end of the respective films. Roald Dahl, a screenwriter of "You Only Live Twice", said he was given a formula to work to
SMERSH (James Bond) grafts, signs of the wound remain in later Bond books). Then, at the end of the novel, Bond's lover and fellow agent Vesper Lynd—in fact a Soviet double agent—commits suicide when she learns that a SMERSH agent has her under surveillance and that the organisation is planning to kill her. As a result of her death, Bond swears vengeance upon SMERSH, which he calls "the threat behind the spies, the threat that made them spy". His revenge begins in the second novel, "Live and Let Die", wherein he becomes highly interested in disrupting Mr. Big's financing of Soviet operations upon