Infinity's Ladder — Patricia Gallagher

By outrageous chance Trellia and her lover Rydin have become integrated with Infinity's Ladder, an algorithm that will bring them step by step to their destiny. They are delighted to be alive after their astonishing, mysterious arrival on planet Tavos. Their mentor Oarsh's account of it does not seem true. Nonetheless, he intrigues them with possibilities and his philosophy about the Universe's creation. Young and bold, they search for a way back to their own planet; this exploration leads them into one perilous situation after another.
When a deadly virus fells Trellia, a human clone saves her life; that brings her to the attention of
Te Hara, the clone's creator. He hates Oarsh, and with Noshdon, an avaricious high priest, accuses Oarsh of crimes against the State to be rid of him. Their plot accidentally leads to a bolt from the blue; the origin of Rydin, Trellia and their life's purpose.