When a station is played and charm declared, that station is rendered attractive to all token-holding players within the same quadrant, who are forced to move towards it in the most direct route possible until charm is negated.
The secondary effect is to reverse rotational influences currently affecting all stations in the same zone. When played in conjunction with a bi-lateral straddle, charm can have devastating effects on inter-zonal movements (see Berners-Lee vs. Rubia - 1989). Care must be taken to avoid leaving oneself exposed to charm for more than three moves subsequent to initiating it.
[PJ]