Former Cardiff City ace Mason, 27, is a free agent having just been relased by Premiership Wolverhampton Wanderers.
Mason began his football career at Home Park before joining Cardiff in July 2011 for £250,000 on a three-year deal.
He joined Wolves in early 2016 and has had loan spells in recent seasons at Burton Albion, Colorado Rapids and Saturday's Argyle opponents Portsmouth.
Adams also revealed popular striker Joel Grant (thigh) had operation yesterday and is hoping to be back before the end of the season.
