What made you watch this drama - plot, cast, or writer - director ?

I see Han Hyo Joo, I click. She does tend to pick projects that are precisely the type I love and enjoy and even if not, I’m guaranteed to like her character portrayal and the choice of character she’ll play. 

I respect the writer for Stranger, though her last drama Grid felt like an unfinished manuscript pushed into production before it was ready for an audience. Also I’ll give most sci-fi thrillers a try. 

and then the plot... I'm a biotech so I had to see how they would develop this plot.