From NBC's official press release:
Season finale - The Scranton Office represents at the company picnic.
Oscar nominee Amy Ryan (Gone Baby Gone) and Idris Elba (The Wire) guest star.
It's the annual Dunder Mifflin company picnic and Michael (Golden Globe winner Steve Carell) and Holly (guest star Amy Ryan) are reunited, and Michael has some big plans for her. Meanwhile, the office competes in the picnic's volleyball tournament.
The Office also stars Rainn Wilson, John Krasinski, Jenna Fischer, Ed Helms, Leslie David Baker, Brian Baumgartner, Kate Flannery, Mindy Kaling, Angela Kinsey, Phyllis Smith, Oscar Nunez, Creed Bratton, Paul Lieberstein and B.J. Novak.
Source: NBC
(Image courtesy of NBC)