D&D 5E Starter Set : killing someone unconscious (spoilers)

[Nemio]

I'm preparing the second session of the Starter Set and have a question about the hostage situation that might come up in Cragmaw Castle if my players end up going there.

It mentions that the Doppelganger wants to collect the map and kill Gundren who is unconscious, action on order of the Black Spider (BBEG)
If a fight breaks out and King Groll is killed it says that the Doppelganger tries to kill Gundren and flee with the map.

I want to be ready for this situation.

Gundren is considered a dwarf Commoner and so he has 4 (1d8) HP
He is unconscious and stable at 0HP

The Doppelganger has Multi-attack and deal 1d6+4 damage.
An attack against someone unconscious has advantage and if it hits it deals critical damage.
If just one of the 2 attacks hits (which is very likely) then Gundren reaches his negative max HP and dies instantly.

Giving him max commoner HP (8) might lower the risk since then both attacks would need to hit but that's still very likely with advantage.

(I'm not even sure how I would narrate that someone would "miss" an unconscious opponent. Any ideas?)

That means that if the Doppelganger acts before the players then they have to watch helplessly while he is getting killed.

That doesn't seem fun.
Is there any way to give them a final try at stopping the murder attempt while staying within and/or bending the rules?

Maybe I'm overthinking this

 

[delericho]

It mentions that the Doppelganger wants to collect the map and kill Gundren who is unconscious, action on order of the Black Spider (BBEG)
If a fight breaks out and King Groll is killed it says that the Doppelganger tries to kill Gundren and flee with the map.

That means that if the Doppelganger acts before the players then they have to watch helplessly while he is getting killed.

That doesn't seem fun.
Is there any way to give them a final try at stopping the murder attempt while staying within and/or bending the rules?

First up, I'm not sure I see the problem - if the Doppelganger only tries to kill Gundren if King Groll is killed, surely his winning initiative isn't an issue. He'll still wait until KG is dead, so the PCs will have at least some actions first?

Even if not, there's an easy way to avoid the "PCs watch helplessly" issue - just have him do something else first. Perhaps he spends a round grabbing some vital gear in preparation for making his escape, or he elects to launch a ranged attack at a PC, or something.

(I'm not even sure how I would narrate that someone would "miss" an unconscious opponent. Any ideas?)

He bends to rip out Gundren's throat, but by outrageous fortune his claws get tangled in Gundren's collar (or beard) and so miss their mark. Or he gets distracted at a key moment and what should have been a lethal blow turns into a mere scratch.

Something like that. Bear in mind that it's only an issue if four dice all indicate a miss (two attacks, each with advantage), so it's already a very unlikely scenario. So, feel free to describe a freak occurance that makes his attack go astray!

 

[Nemio]

Yes, that's true.
It would happen later in the fight and only in case the Doppelganger gets to act first after another PC kills Groll.

Unlikely perhaps but I just want to be prepared.

The way the adventure overview in the DM booklet is written also seems to imply that Gundren is supposed / likely to be killed.
Something along the lines that they have to avenge his death, I don't have it here.

I suppose the Doppelganger is already engaged in the fight at that time so I could have him Disengage and run towards Gundren to show his intentions.
He would corner himself that way though (Gundren is lying on the floor far from the door) and it mentions he will fight to the death if that happens.

Nice description of the possible miss, thanks.

 

[Ricochet]

I did it using death saves, after the doppelganger stabbed Gundren once (first fail). My characters came one initiative too late to save Gundren once the doppelganger was dealt with. It was a great encounter, and the fact that Gundren died was a talking point for the rest of the campaign. It was a definite highlight, and a "we can't always save the day, but dammit, we'll keep fighting!" moment for the players.