My translation of the plot summary:
Chris Redfield, member of the biohazard counterterrorism organization BSAA, infiltrates a mysterious mansion belonging to an organization involved in the sale of illegal weaponry. During his investigation, he confronts Glenn Arias, a criminal on Interpol's watch list. Chris witnesses an unbelievable sight, and Arias eventually manages to get away.
Meanwhile, Rebecca Chambers, originally a member of the RPD S.T.A.R.S. and now a university professor, is researching and investigation a mysterious incident in which "the dead are resurrecting and becoming more sinister."
Based on her investigation, there is a "new-type virus" involved, and Rebecca's efforts to uncover the truth lead her to successfully developing a cure. Immediately after, a mysterious person infiltrates her laboratory, and Rebecca is nearly killed before Chris and the BSAA save her just in time.
After this attack, Chris and Rebecca go to Leon S. Kennedy of the US government's DSO because Leon is the person most knowledgeable about it.
Chris and Leon thus meet again.
Both of them believe Arias' true motive is "bio terror." Together with Rebecca, they travel to New York in order to stop Arias' plan and save humanity.