I'm not sure, but this sounds like something from "Mostly Harmless," which was the HHGTTG novel I only read once. That novel had a side plot about Arthur's "im

I'm not sure, but this sounds like something from "Mostly Harmless," which was the HHGTTG novel I only read once. That novel had a side plot about Arthur's "immortality" and how his choices impacted a character that was introduced in "Life, The Universe, and Everything."