Move segment
Chiron, the Boggsmen, and then Walfried rush for the cover afforded by the boat hull. The dragon pursues.
Missile Segment
Will the dragon breathe or bite? 2d6=9, so it will breathe. The ref rules the boat hull will serve as hard cover (once only), so those cowering behind are spared.
Chiron will hurl his lantern; the ref presumes he will lob it indirectly so as not to expose himself to the deadly breath-weapon. Indirect fire is reckoned to be at long range or -4 to hit. Chiron throws 1d20=19! -4 makes 15 which is enough to hit AC 4. M&T has all dragons AC 2, but DD4 grades them by age and has AC 4. So... (ponders whether armor even matters here...) let's call it a hit.
OD&D is not specific about burning oil damage, but Holmes has 1-8 hp on the first "round" and 2-8 hp on the second "round". So one "normal hit" for each of two periods. That missile fire occurs outside of combat rounds doesn't quite gel, but we'll go with it. (Ref notes also that Holmes treats hurled oil as a hand ax, requiring a base throw of 11+ to hit a man-sized target, regardless of armor). So... Chiron's initial damage throw: 1d6=3.
Melee Segment
The dragon had to close, so there is time for only two melee rounds this turn.
First Round
The four Boggsmen have their spears set against the beast, so they'll have the first strike. Should they chance a hit, their spears will do double damage--and much hope rests in this!
I have the names Werner, Klaus, Anton, Schlags jotted down. Not sure of the other two, but they're slag now anyways.
4d20=14, 16, 18, 2. By the Hairy God of Rat-arsed flunkies! Anton has scored a famous hit (dragons are impervious to normal missiles, but not all normal weapons. Klaus also has thrown 16, which hits a DD4 adult black dragon (but would have missed an M&T dragon with AC2).
So it's two hits, each doubled (due to M&T p31 "if something impales itself upon the spear damage will be double or even treble if the force is sufficient." DD talks about double damage only).
Anton 1d6=4 doubled is 8.
Klaus 1d6=2 doubled is 4.
The dragon attacks as six men.
6d20=6, 14, 3, 7, 15, 4.
The 14 and 15 are targetted at: (1=Werner, 2=Klaus, 3=Anton, 4=Schlags, 5=Walfried, 6=Chiron) 2d6=1, 4 so 14 vs Werner and 15 vs Schlags. That's two hits. Ref dices for their hp 2d6=2, 3. Dragon damage 2d6=3, 6. Two men down.
Walfried attacks last: 1d20=9 it's a miss.
Ref applies Chiron's 3 hp fire damage in this, the first round.
Second Round
The initiative now goes to the attacker (unless any of a bunch of circumstances apply, which they don't).
So the dragon attacks again!
6d20=3,18,6,2,6,12. That's exactly one good throw from six. Who is targetted? (1=Klaus, 2=Anton, 3=Walfried, 4=Chiron) 1d4=1 It's Klaus! Ref dices for his hp 1d6=1. He's gone. Dragon damage 1d6=3. Klaus is slain.
Anton and Walfried attack: 2d20=11, 19! Walfried hits! Will it be a death blow? 1d6=SIX!
Chrion's remaining fire damage 1d6=SIX!
The dragon is slain.
As are Werner, Klaus, and Schlags.