Kill the poltergeist

 is an optional, non-repeatable side mission featured in S.T.A.L.K.E.R.: Lost Alpha.

Overview

 * After exterminating various infestations of mutants, usually at a distance from Sid's bunker and frequently potentially lethal; Sidorovich offers what appears to be a 'milk run'.

Trivia

 * Bringing a Sawn-off Double-barrel Shotgun or something similar is an advantage, as is maintaining the ability to run.
 * The apparent anomaly with the mission duration is quite genuine and equally inexplicable.