Detective Comics Vol. 1 (1937-2011; 2016-) #831

Plot

Writer Paul Dini — creator of Harley Quinn — returns with art team Don Kramer and Wayne Faucher (JSA)! A bizarre incident forges a temporary alliance between the Dark Knight and his daffy-but-deadly adversary Harley Quinn. Forget everything you think you know about Dr. Harleen Quinzel as Batman uncovers long-buried secrets from his enemy's unknown past.