'When Calls the Heart': Oil Explosion Forces All of Hope Valley Into Panic (Exclusive)

In ET's sneak peek at Sunday's upcoming episode of 'When Calls the Heart,' an oil explosion causes the entire town of Hope Valley to erupt in panic.  Mountie Nathan Grant immediately heads off on horseback to investigate the catastrophe while Bill agrees to meet him there after calming the townsfolk. Fiona offers to help, but Bill tells her to remain in Hope Valley. 'When Calls the Heart' airs Sundays at 9 p.m. ET/PT on Hallmark Channel. Category: TV, NEWS