When the Royal Physician is murdered, the only witness, a once promising young surgeon, must save the Queen's Secret Court from a strange race of alien streetwalkers.

By, George, I think you’ve got it!

The posted logline (not your “or” one) sounds to be spot-on after several attempts at rehabbing the original generation. This one seems to be perfect- you started off with “When” (“After”, “While”, “Because” are also excellent logline starting points, as it forces you to “ask” and “answer” the question), you have under thirty words (27), you include: the Lead (promising, young surgeon); Obstacle (aliens); Goal (saving the Queen); Loss (or stakes- risking one’s life); Irony (missing, but inciting incident is clear- death of royal physician); the “New” (unique concept, or “hook”- aliens mixed with Royal Family story); and the Enemy (antag- alien streetwalkers).

You might want to consider two things: hyphens instead of commas between “a promising, young surgeon”, and elevating the descriptive terms like “promising, young” and “strange”. Those phrases are often over-used and don’t elicit enough dramatic impact. Other than that, it’s very good! Nice work, after many previous struggles!