Erik Klemetti starts to question his decision to become a geologist when a 20,000-foot volcano in Chile, proves difficult to tame, and explorer George Kourounis prepares to enter a fiery sinkhole known as the “Doorway to Hell.”

Science writer Kate Sheridan falls in love with a man who suffers from paralyzing headaches, and math teacher Giselle George-Gilkes is on a trip with her students when she receives terrible news from home.

Gail Thomas clashes with her oncologist while deciding how to fight her cancer, and as a marathon runner, Pierce McManus prides himself on his toughness — but then he begins coughing up blood.

Science journalist Sushma Subramanian experiments with haptic technology to connect with her long-distance fiance, and Nick Andersen’s type 1 diabetes begins to affect his dating life.