Any level PCs, but the players must never have played them before. Specifically tell them not to worry much about character backgrounds, just have a name and description with 2 visual details.
The PCs are all guarding a nobleman. Tell the players not to worry about why.
Assassins burst in… and try to kill the PCs, screaming for the nobleman to run.
The first time each PC is injured, that PC is revealed to be a doppleganger.
The doppleganger PCs literally don’t remember their past, or why they were standing around the nobleman…
(Do you enjoy the content on this blog? Why not become a patron, and support more free material!)