Other than the previous scripture I noted that says the lake of fire [is] the second death, here it says it plainly what happens to those who don't believe.
Romans 6:23
23 For the wages of sin is death, but the free gift of God is eternal life through Christ Jesus our Lord.
Luke is unclear when it says:
Luke 12:5
5 But I will show you whom you should fear: Fear him who, after your body has been killed, has authority to throw you into hell. Yes, I tell you, fear him.
But Matthew is clear:
Matthew 10:28
28 And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell.
Destroy definition: to reduce (an object) to useless fragments, a useless form, or remains, as by rending, burning, or dissolving; injure beyond repair or renewal; demolish; ruin; annihilate.