Secundus and Tertius have been playing with the hose and with water balloons in the backyard. After a break indoors -- during which Secundus is suspiciously elusive -- Tertius is persuaded to step outside the backdoor and wait.
A card descends on a length of string from the upstairs bathroom window. On in is written "Look up."
(On the reverse, just in case, it reads "Look on back of card.")
Tertius looks up.
A water balloon drops on his head.
Nice to know that an education based on Chuck Jones cartoons hasn't been wasted.