Canon Background
https://awoiaf.westeros.org/index.php/Bryen

In-Campaign
Bryen was acting as messenger for his lord, returning to Baelish lands when he was stopped by Ser Dolins. The old knight questioned what he was doing and Bryen was cooperative, until Dolins demanded he return to Snownook. Bryen attempted to depart but was intercepted by Dolins. When Ser Maelys, Ser Cedric, and Gregoriy arrived not long after Bryen acquiesced and turned back to Snownook (with Ronnel’s letter about grazing rights still in his satchel). After his role of messenger was confirmed with Lord Jasper Bryen was released, and was none too pleased about the delay (but did his best to hide it).