It’s called Sentinel’s Shadow and it quite simply fantastic!
Here’s its blurb:
“What were the chances that that on November 23rd, 1963 President John Kennedy was shot and killed while a second John Kennedy was gunned in small town Beatrice?
So began the adventures of Hawk and Dec as they become involved in a complicated conspiracy for a young girl’s murder, but an unforgettable quest that might very well lead to Jesse James’ stolen gold.
If the Knights of the Golden Circle don’t find it first!”