”Thing” is a dialogue-heavy thriller so smooth that it reads, scene for scene, like a screenplay — except with better descriptions. After a darkly nostalgic prologue in which two white 11-year-old girls in Baltimore kidnap a black baby, we flash forward seven years, when the teen perps have lost touch after being released from the custody of the state of Maryland. When another baby disappears, the ex-cons become suspects. It’s easy to get hooked on the story. But despite Seinfeldian observations about, say, hoity-toity patrons at bagel shops, Lippman stumbles when trying to make us care about her characters.