Left to right:
1. temperature of a plate subject to a point source firing at time t=0 (this could be e.g. a laser pulse).
2. temperature of the plate with a "kite" object present. As you can see the isotherms, or temperature contours, are deformed by the presence of the object and this can be used by an observer to detect and locate the kite.
3. the kite object is surrounded by our active cloak. Now the isotherms look exactly like the ones in the case where the object is not present, which hides the kite object.