Chuck Season 3 Episode 19 (Chuck s03e19) with title “Chuck Versus the Ring: Part 2″ airs on Monday, May 24th 2010 at 09:00 pm via NBC.
Here is summary for Chuck Season 3 Episode 19 :

Shaw returns to threaten everything that Chuck holds dear as his friends, family and the woman he loves are all put in mortal danger. Elsewhere, Chuck must find Shaw and stop him before his own world gets torn apart.

Few hours after original series aired on TV, online streaming video for Chuck Season 3 Episode 19 usually available on Net and of course, if video available, as soon as possible will show you where you can watch this episode for free.