Drama! Someone has stolen a whole bunch of stuff from Downton Abbey and it's up to you to get it all back. And figure out who did it in the first place, of course.
What that basically means is you get to wander around the estate, looking for clues and questioning the residents. Downton Abbey: Mysteries of the Manor is a hidden object game, sure, but it's a hidden object game that's set in Downton-freaking-Abbey. Don't act like you're not at least a little curious.
You can download Downton Abbey: Mysteries of the Manor for free.