The CIA, with help from Howard Hughes, raises a Soviet sub that sank but that may have been planning on launching a nuclear missile on Hawaii to create a Chinese - US nuclear war. Sub and missile match that of recent sale to China.
Speculation that Captain First Rank V. I. Kobzar self destructed the missile in the sub to stop the launch being forced by KGB linked military on board. Quite a bit of monitoring data that backs it up.
Some just believe it was a accident.
The USS Scorpion sub lost shortly later, believed sunk by the USSR.