A hovering trail of vapor set against vibrantly colored skies recurs in William Monk’s new series, “Untitled.” What does it mean? The artist has said, “I camouflage the content of my paintings. I want to be cryptic.” But he refers to various influences: Pompeii and volcanic spill, a sequence from a sci-fi movie, a fuel trail from a missile. The point? His works are suggestive, they send the viewer wherever the viewer wants to go. In Monk’s words, they capture this “silenced and beautiful apocalypse.” —E.C.