In a remarkable year, two gritty teams of hobbyist cavers are poised to break records for the longest and deepest caves in Canada. After discovering a flooded underground chamber, Katie, a daytime accountant, becomes obsessed with returning to the Bisaro Anima cave in the Rockies to push the caving depth record. At the same time, a passionate Vancouver Island team is attempting to link two tunnel systems to create the longest known cave in the country. From abyssal, muddy crawls to heart-pounding, vertical pits and underwater squeezes, these are places where no person has been before.