Reach a certain DECIBEL and bombs will explode! Former Lieutenant Commander Kang Do-Young is revered as a national hero for saving many of his men in a submarine accident, but he couldn't save them all. Now he must face off against a terrorist with a sound sensitive bomb. Can he save everyone this time? He must race against the clock to track down the terrorist and save his family. Amid this impossible task, dark secrets the Commander left buried in the sea resurfaces.