If you’ve ever held a penny, memorized the Gettysburg Address in school or visited that big marble memorial, you know President Abraham Lincoln. But you’ve probably never heard of Abraham Lincoln II, the grandson the president never met.

The story begins with Lincoln’s end. On April 14, 1865, the president’s son, Robert Lincoln, visited the White House, fresh from serving in Grant’s army. Robert E. Lee had surrendered days earlier and, with the Civil War winding down, the president was ready to unwind. He invited his eldest son to accompany him to a play that evening.