OOC:
In this situation, I'd say Janice could
- go for a MANIPULATION roll, to try and get Holroyd to agree to her point of view (it's then an opposed roll, Janice would need to get more successes than Holroyd for her to change his mind about killing the doctor.
- a COMMAND roll to order him to stop - I'd make that vs Holroyd's STAMINA (he would need to resist his programming, presumably, to obey orders)
- a CLOSE COMBAT roll where you need to get at least two successes, so that you can pick the "opponent is knocked to ground" or "hold opponent in a grapple" stunt with the second success
All coming with the risk of triggering a panic from the added STRESS dice.
Or pitch another approach if you like.
And to specify the order of action here between Holroyd and Macwhiir, please make opposed MOBILITY rules.
Holroyd has more, there are an equal number of successes -> Holroyd makes his attack on the doctor, then it's Macwhirr's turn.
Macwhirr has more -> she gets a chance to act before the attack reaches the doctor.
After that you'll alternate actions.
Free-styling it with the rules a bit here - they're not built for PvP.
If we were live, I'd discuss with you how we want to do this, but to keep the PbP moving, I'm going to rule this way unless someone really wants us to do it differently.