Complex sentence: The "Enterprise" crew, able to locate Riker with Mirasta's help, bring both Riker and Krola back to the ship; they discover that Riker's phaser was only set to stun, and Krola was in no real danger.
Split into simpler sentences: The "Enterprise" crew bring both Riker and Krola back to the ship. They are able to save Riker's life, and discover that his phaser was only set to stun, so Krola was in no real danger.