Therese doesn't like being stuck on the sidelines, especially when the entire pantheon is in trouble.
Hypnos and Jen aren't married long when they realize something's missing: they both want to have a child, especially when they see how happy Therese and Than are with their twins. But the creation of new gods is against the rules, and they aren't willing to give up their immortality.
Hypnos goes to Mount Olympus to offer Zeus a deal. He'll make it his mission to find out the source of the recent attacks on Gaia--horrible earthquakes that have already released two monsters from the Titan Pit--if Zeus will agree to let him and Jen have one immortal child.
Because the attacks are getting humans killed and none of the other gods have been able to discover a lead, Zeus, in his desperation, agrees. But this new quest just might get Hypnos swallowed and trapped for all eternity, and there seems to be nothing Therese and Than can do to stop it.