Any story actually dealing with the Brood (rather than having it as a background element of Weird Stuff) in New Mutants will therefore not only see our team fail to deal with the problem adequately, but end with them not even recognising one.
And so we get #3, where Dani becomes aware the a monster, nobody believes her, it manifests in all their presence and then... it is revealed to all be a dream (caused by Dani's fear powers, under an outside influence). They even get as far as hypothesising that Xavier is linked. And then they go and see some TV, the five of them.
So, that moment in #2 where Stevie realises the only person who could have run the advanced training problem in the Danger Room, is Xavier, is just plain wasted.
Couple of other bits in #3: Moira and Sean talking about having children again, with Moira moping about not having had a son by Xavier. And Illyana, who Sean catches doing some kind of ritual to do with Belasco. Whatever it is, that can't be good.
#167 itself starts quite hilariously. The X-Men, having concluded there is a Brood egg in the Professor in #166, go straight for the mansion (bypassing the Proto-Utopia island, I suppose, although maybe they went there first and that's why they're in such a hurry), and then attack the group of children in the common room. This is not your usual superhero misunderstanding - the X-Men know full well that the kids are new students of Xavier's. It's just that subduing them is going to take less time than explaining matters.
The New Mutants prove less of a pushover than Cyclops was expecting, but ultimately are defeated. Just in time for them to find Xavier in the final stages of Brood incubation and watch him turning into a Brood Queen. The Brood beats the boys (Cyclops, Wolverine, Colossus and Nightcrawler) to a standstill, but then the artillery arrives in the form of Warbird and Storm, and the Brood Queen is taken down.
Just as they are about to kill it, they discover that Xavier's personality still exists within, and spare its life. By an amazing coincidence, the Starjammers have the technology to clone Xavier's body, and then "transplant" the mind. This works very well, and even gives him shiny new legs. Until he tries to stand on them, they buckle underneath him, and he discovers his mind needs time to adjust.
And what are we to make of this notion that Xavier has drawn together the New Mutants specifically to lay eggs in, mentioned in #4? Well, if you examine what happened more closely, it doesn't make much sense. Xavier was depressed after the apparent loss of the X-Men and Lilandra, and the idea to train Karma was practically forced on him by Moira, who also provided Rahne. Psyche he got a letter about, and then he only picked up Cannonball and Sunspot because they got entangled in Pierce's schemes. So, at what point did the Brood's influence manifest? If we can blame anything on it, perhaps it's the reason Xavier has decided not to form another team of X-Men to go on missions, but instead to keep the tasty tasty children safe and close.
#167 is also the issue in which the issue of Scott and Alex's grandparents are raised. Turns out, they have some, which is complete news to Scott, as if he's never thought about the issue before. He's not a John Doe, he knew the name of his parents - it's never occurred to him to check? Why, for that matter, wasn't he placed with them instead of being put in an orphanage?
And finally, Lilandra was stranded too, with the X-Men. Gladiator turns up, wanting an audience with her. He declares Deathbird unfit to rule, and suggests a space rebellion! And sets us up for a bizarre page in which Lilandra goes and gives Reed a piece of her mind for refraining from killing Galactus, apparently intended as a bit of cheeky revenge at John Byrne, after Byrne retconned the Doom in #145-#147 as a Doombot.
Finally, coming to New Mutants #4, it's one of those unusual X-Men stories where the only superhero element is the good mutants themselves. The "villain" of the piece, who has been making harassing phone calls to Stevie, is, shockingly, the new character introduced on page 2. Edgy stuff.