(n.) The act of pursuit.

aggravation annoyance bad news bedevilment bore bother botheration bothersomeness chase chasing crashing bore devilment difficulty downer drag exasperation follow follow-up following harassment harrying headache heeling hounding hue and cry hunting molestation nuisance persecution pest problem prosecution pursual pursuance pursuing pursuit quest searching seeking sequel sequence series shadowing stalking tailing tracking tracking down trailing trial trouble vexation vexatiousness worriment worry