See if you can spot what's wrong in these photos of crowds

Need help? Cass writes: ""It's a spacial trick. The people around the central figure holding the balloon form a rough circle that isolates him."

Cass explained this series in an interview with Vice: "The first picture looks ordinary enough: people waiting to cross the street, looking off to the left. But it turns out that it’s all men on one side, all women on the other."

"[T]he second picture ... is made up from the same set of exposures covering an hour or so, which shows families holding hands," Cass says. "It’s as if they procreated in the middle of the street."