Today’s strip gets a “time travel” tag and a “retcon” tag, because both of those things appear to be happening!
This is lifted wholesale from the Fatty Arbuckle case, by the way. Dashiell Hammett actually was a Pinkerton man in the late 1910s and early 1920s and he did claim to be a part of the Pinkerton team hired by Arbuckle’s defense attorneys, though some historians doubt his involvement was significant if it even happened at all.
How this squares with the timeline of silent film star 1940s icon Butter Brickle Brinkel’s trial is unclear… but all timelines in the Batiukverse are about as clear as an oil spill.