With the help of flashbacks and eerily similar storylines, we see Chuck relive the start of his career as an asset/operative - only this time from the other side of the table.
The naive geek "target" is a carbon copy of Chuck of three years past, and Chuck gets to step into Sarah's shoes to befriend the asset.
But unlike Sarah, Chuck is actually able to do his duty when the time comes to burn the asset, despite the anguish it causes him.
Chuck's transformation over the last episodes from earnest young geek to gradually more hardened operative is interesting and well played, and Sarah's reaction is equally engaging.
There are a lot of painful moments and insights - Chuck's smooth lie to his sister, Morgan and Ellie's realization that their favourite geek is hiding something from them, Sarah wondering if Chuck is still the man she fell in love with.
I did notice that the show kept one big difference between Chuck and his carbon-copy asset - while Chuck is an allround good guy who has always been willing to lay it on the line for the good of his country/friends/the world, Manoush was unwilling to see the consequences of his actions and choices - as long as it would make him rich.
Which is why it was right for Sarah to try and keep Chuck out of secure storage - and why it is right for Chuck to burn his asset...