While investigating the resurgence of an old flu strain that resembles the Spanish Flu, the team finds a reclusive family of drifters in hiding, who all look like they came straight out of the 1910s, and may or may not be vampires.
Investigators are exposed to a highly contagious virus that's been out of circulation for 70 years when they research an anachronistic family that carries---but is immune to---the virus.