The American Civil war inspires the heart of conflict in “Mercy Street,” an upcoming medical mini-series from PBS, which centers on a hospital in Union-occupied Alexandria. The drama, which screened at Culbreth Theater as part of the Virginia Film Festival, is riveting and brings Civil War-era Virginia to life. “Mercy Street” is based on the lives of nonfictional historical figures like Mary Phinney (Mary Elizabeth Winstead), a nurse who struggles to reconcile her anti-Confederate sentiment with her responsibility as a nurse. She clashes with others at the hospital like Dr. Jedidiah Foster (Josh Radnor), who teaches her when people are dying, the color of their uniform does not matter: “blood isn’t blue or grey.” “Mercy Street” expertly balances the typical thrills of a medical drama with the complicated political and social turmoil of the South during the Civil War. It does not hold back on showing the horrors of war, but it also infuses enough humor to keep the show light. “Mercy Street” is also visually stunning; it has all the sumptuous costume and set design one would expect from a PBS period piece. The characters of “Mercy Street” are complex and dynamic, which is no small feat given the sprawling ensemble cast. These characters are brought to life through strong performances throughout the cast. As the conflicted Mary Phinney, Winstead is compelling to watch, as she skillfully portrays both Phinney’s uncertainty and determination to prove herself. She is a solid lead and someone the audience can root for. Radnor’s character quality is a far cry from that of his most well-known work on the sitcom “How I Met Your Mother,” but he excels in the more dramatic role. Dr. Foster is a complex character, and Radnor capably portrays the nuances of the role. Radnor immerses himself in the part, and it pays off. Newcomer Hannah James, as privileged Southern belle Emma Green, is the breakout star on “Mercy Street.” Her character must quickly grow up and face the harsh realities of war, and James is earnest and strong-willed as she portrays this abrupt loss of innocence. Green has the most potential to grow as the season progresses, and James seems more than capable at portraying that growth. “Mercy Street” is not perfect — it falls victim to the occasional cliché and cheesy line — but if the premiere is any indication of what the rest of the season will bring, it is not to be missed.