Please note how casually Jekyll is eating that sandwich.
In an earlier version of the script, Lanyon's flashback was a direct reference to a scene from Strange Case where Utterson (here played by Lanyon) confronts a reluctant Mr. Hyde in the alleyway behind his laboratory. Elements of that scene will come into play in later chapters, but for the present moment, the scene kind of lagged and didn't have a super clear point beyond "hey, it's that scene from Strange Case that doesn't get mentioned a lot" and "Lanyon is pretty easily freaked out."
IRL Update: My harddrive failed! I don't super know why, except that according to the tech guy I brought it to, this happens from time to time on iMacs from around 2013. Luckily, my files were backed up (knock on wood--I won't know absolutely for sure until I get them all added back in) but I'm stuck using my computer at the office for all my comic work for at least the duration of the week. It's kind of creepy being at the office at midnight.
Moral: Back up your files with an automatic back-up program! Ideally, use two.