the thick of something
in the thick of (something)
Very busy; in the middle of or preoccupied with something or several things. Sorry I couldn't make it to your birthday lunch on Wednesday—I'm afraid I'm really in the thick of several big projects at the moment. We're going to find ourselves in the thick of a war with half the world if our president doesn't change his confrontational way of dealing with other world leaders.
the thick of somethingthe busiest or most crowded part of something.
1999 Christopher Brookmyre One Fine Day in the Middle of the Night They'd been in the thick of it, sharing God-knows-what experiences together, from foreplay to gunplay.