IN MEDIAS RES
Here’s that accusative you’ve been waiting for.
In medias res means into middle things. We would say “into the middle of things,” but in Latin the adjective medias and noun res are both accusative plurals.
Perhaps the earliest use comes from our favourite phrase-maker Horace, who talked about how Homer begins the Iliad right in the thick of the action.
nec gemino bellum Troianum orditur ab ovo;
semper ad eventum festinat et in medias res
… auditorem rapit
Nor is the Trojan War laid out in order from the twin egg (ab gemino ovo);
he always hurries to the event and into the middle of things
he snatches his listener
Twin egg? Helen was hatched, according to legend, from one of two eggs laid by Leda.