As a slow action, you can attempt to grapple your opponent. Roll for CLOSE COMBAT. No weapon can be used. The grapple can be blocked. If the
attack succeeds, both of you fall to the ground. The opponent drops any weapon they were holding and cannot move. The only action they can
perform is to try to break free – which is a slow action and requires them winning an opposed CLOSE COMBAT roll against you. While you are grappling,
the only action you can perform is a grapple attack. This works as a normal unarmed attack but is a fast action and cannot be blocked.
So once i have an opponent grappled, i can then immediately make an unopposed close combat attack and damage against them (If i haven't already used my fast action), and every subsequent round if they haven't broken free i can do it twice more. And as their only available action is to try and break free, they can't shout for help (which is a free action, but still an action).
The only thing i might house rule is if the opponent does not see the grapple coming, on 2+ successes on the grapple attempt you don't necessarily both fall prone- allows for a more professional takedown.