Summary:

When Kon died, his friends tried to bring him back. Cassie turned to a sham cult. Tim turned to science. They both failed.

When Bart died, Tim and Cassie held each other back from the ledge.

When Tim dies, Cassie does what she should have done the first time. She returns to her roots. She turns to the Greek gods.

The Underworld.

Or: Tim dies, and Cassie can’t handle it. She sets out to bring him back, Orpheus style.