Step on the Sun

Book 1 in the Council of Three series starts when Amy, Paul and Frank rescue an old priest from rocks thrown by children. As the saying goes, no good deed goes unpunished. Believing that the One Who Tests, God's name on other planets, has sent them to him, the priest shows them how to travel to nearby planets, but there is a condition. They must deliver his staff and journals to his home planet.
Their first trip to other planets has them talking to huge intelligent spiders, and running from a dangerous alien and bandits. The local planets are more dangerous than they were told. A friendly alien guides them to the safety of a fortified village where they learn the galactic language and local customs.
On their next trip they have to rescue the villagers, the ones who sheltered and taught them, from slavers armed with swords and spears. Using the sidearms and shotgun they carry with them this trip is the only way they can survive the overwhelming odds they face.
Back on Earth they feel safer, but they don't know that more than one group on Earth is aware of their travels to other planets. Each of these groups wants that knowledge for themselves. They watch them, and plan their next moves.
On other planets, their so-called friends have instructions to kill all three of them if…