End Of The Rainbow (S06E15)

Nick visits an opal miner named Jackson, bringing along a generator. However, Jackson becomes aggressive and attacks Nick, only to soon struggle with his breathing. He heads to the hospital with his daughter while Nick stays behind to watch the mine. That night, a thief breaks in and makes off with some opals. The next day, Jackson returns to find himself unwell again, prompting David to conduct tests on the mine. Suspecting his former partner Palmer of the theft, Jackson confronts him at his own mine. David follows and discovers them in a heated fight when suddenly the roof collapses, trapping all three. Just in time, Tom and Nick rescue them. Ultimately, David learns that Jackson is allergic to a fungus in the mine, preventing him from continuing his work, leading him to sell the mine to Parker.