I don't want to spoil the surprise by giving away too many details, but the solo gets to find out about their heritage the hard way*, and the other party is sent to investigate certain developments which are linked to the solo's travails.
The rest of the plot is falling into line.
Our loner needs merely worry about the Dark Stranger who has kidnapped them from their peaceful life and made them wander about impossible vistas while wearing this impressively large gem on a chain around their neck.
The others, back in Amber, find that Uncle Random the King is worried. See, the two red-heads (that's Fiona and Bleys) left on a fact-finding mission of great secrecy some time ago and are now apparently missing. Given what happened the last time red-haired relatives went under the radar for a while, His Majesty is feeling a teensy bit concerned and would esteem it a helpful thing if some of the youngest members of the family would discretely investigate...
* There are so many unknown scions of Amber out there in Shadow, after all. Trite and cliche, I admit, but it works!