Was anyone in the Old Testament saved by faith plus nothing, or was the Law involved?

In the Old Testament, no one was saved by faith plus nothing; the Law was involved. Israel was under the Law from Exodus 20, and a Jew came into a right relationship with God through law and faith. The Law served as a schoolmaster to bring them to justification by faith, not law keeping.

Les explains that from Exodus chapter 20 onward, Israel was under the Law, and while faith was still the operation that brought an individual Jew into a right relationship with God, it was law and faith together. There was no such thing as faith plus nothing until after the Law was totally satisfied at the cross, when Christ died and satisfied its demands. The Law was a schoolmaster to bring Israel to the place where they could be justified by faith, not by law keeping. All through the Old Testament, the prophecies pointed forward to their coming Redeemer, King, and Messiah, so they should have known who He was, but they were steeped in unbelief.

Were people in the Old Testament saved by faith alone or by law and faith?

From Exodus 20 until Christ satisfied the Law at the cross, Israel was under the Law, and the operation of faith brought an individual Jew into a right relationship with God, but it was law and faith, not faith plus nothing. Faith alone came only after the cross.