Double Dot

The  Double Dot  is an anomaly on the Marauder's Map. It is the complete overlapping of two dots (dots represent people). When people stand right next to one another, their dots appear as a Venn diagram and their names can still be seen, but not so with the Double Dot. The names are one atop the other and it is impossible to read both names. The cause of the anomaly occurs only when someone is possessed.