  We prove that every nonabelian free group has a finitely generated isolated
subgroup which is not separable in the class of nilpotent groups.
  This enables us to give a negative answer to the following question by D.I.
Moldavanskii in the "Kourovka Notebook": Is it true that any finitely generated
$p'$--isolated subgroup of a free group is separable in the class of finite
$p$--groups?
