in medias res Look up in medias res at Dictionary.com
Latin, literally "in the midst of things," from medias, accusative fem. plural of medius "middle" (see medial (adj.)) + accusative plural of res "a thing," from PIE *re- "to bestow, endow." From Horace, in reference to narrative technique:
Semper ad eventum festinat, et in medias res,
Non secus ac notas auditorem rapit (etc.)