Salvation is by grace through faith.
Salvation is not gained by good works, and it is not lost by bad works. Works are important but they do not make up salvation. Anyone who is truly saved will have some good works, but if someone believes and then starts falling away, their failure will result not in the loss of their soul but in the loss of their rewards. I have a Bible study from I Cor. It is important to understand the importance of good works in regards to the rewards of believers and the possible loss of such rewards.