Melanie Kraft worked as a CIA analyst for CIA during the events of Locked On. In her spare time, she compiled a memo on the Muslim Brotherhood regarding the differences they show in public, depending on whether they use the english, or a native language. When she showed that paper to her CIA superior, she ran into problems, as the memo concluded that the Brotherhood were close to islamic terrorists. This raised the wrath of CIA deputy director Charles Sumner Alden, a politician close to Ed Kealty, who held that the Brotherhood were friendly to the US,
On the other hand, the memo raised the attention of Mary Pat Foley, at the time deputy directory of the National Counter-Terrorism Center NCTC , who contacts Melanie Considering Melanie to be a prime asset for an intelligence agency, Mary Pat persuades her to switch to NCTC. When Jack Ryan, Jr.visits the NCTC, Mary Pat acts as a match maker, telling Jack that Melanie is "single" and "lives in Alexandria". Melanie and Jack start dating. In the epilogue of Locked On, it turns out that Melanie is providing information on Jack to someone else. In particular, she has deduced that Jack's "business trip" was actually participation in the events in Pakistan by pretending that "Khan", the second-in-command of Riaz Rehan would be on the run. (Jack forgets to pretend that he doesn't know "Khan".)
During the events of Threat Vector, Melanie and Jack sre still dating. However, Melanie is blackmailed into spying on Jack by the fact that her father, a forner USAF colonel unknowingly leaked intelligence to Pakistan. (He had a relationship with a woman he believed to be Palestinian.) When Melanie is forced to plant a trojan in his phone, Jack becomes aware of the fact. He believes her to be a chinese spy. Likewise, Melanie is fully aware of him lying to her about his doings (although she's got a high security clearance, Jack can't tell her about the Campus) and they break up.
At the time, Melanie is threatened to be killed by Center and his Ghost Ship organization, so Jack asks the retired John Clark to look after her. When John is called out of retirement to the Campus, he takes Melanie with him. They arrive right after the chinese assassins who killed several Campus employees. John is able to overcome the remaining assassins, although Melanie is forced to save his life in one case by shooting down an assassin.