Thanks everyone. Here’s more detail.

AAA is to city one on day 1. BBB is to city 2 on day 2. CCC is from city 2 to home (origination for AAA) on day 3.

And technically, he could cancel his return to home train ticket for a full refund and just move his CCC return flight from day 3 to day 4, so it’s a bit more complicated after learning (tonight) that new wrinkle.