The Dungeon #155 additions to Keep on the Shadowfell are by Peter Schaefer and, with all due respect to the man, he just keeps getting it wrong.
Side Trek 3, entitled "Graveyard Exterior", takes place immediately after the Dead Walk interlude. It turns out Kalarel has come to the (correct) conclusion that Ninaran is rather crap, and rather than relying on his Obvious Spy to take out the players alone, he's sent reinforcements - specifically, a one-of-a-kind animated corpse called Maw, and a small legion of zombie minions.
I've mentioned before that Kalarel is rather rubbish, so it's no surprise that Maw and company not only don't get to Ninaran in time to help, but fail to find any sort of beneficial terrain whatsoever. Players leaving the graveyard find the monsters milling around aimlessly in a largely barren field.
Okay, let's talk about the good before we launch into the bad. Maw, as a named undead, is a welcome bit of spice in what has otherwise been a dull blend of zombies and skeletons. If you're going to run several encounters around the same monster theme, you absolutely need to throw some personalities in there to differentiate the battles.
Maw's great. In addition to his evocative name, he also has an encounter power that lets him spawn four zombie minions in the spaces adjacent to him, which makes for a nice surprise for any solo characters who attempt to tank him. He's also got a ranged attack that lets him slide a target in a way that specifically provokes opportunity attacks from his allies.
Unfortunately, like Ninaran, he's relatively fragile, and if you've got a ranger in your party he'll be dead before he can show off what he can do. Also, as the centerpiece of this encounter, he's completely wasted on a map that offers him no favourable terrain whatsoever.
One thing I like about the Graveyard Exterior is it's entirely minions. The fun of minions comes from smashing them to bits at high speed. There's 18 of them here, plus another 4 from Maw's power, so if your players have ever had the slightest interesting in battling a real zombie horde, this is your chance to deliver.
The main problem with the encounter is this. The Dead Walk didn't need a follow-up encounter. It's almost perfect as a one-off battle. By the end of the interlude, the players are likely sick of zombies, and want to take a moment to feel good about killing Ninaran. There's no better way to ruin your session than by following something that worked with its identical and monotonous clone.
It's worth noting that nobody here except Maw has a ranged attack. Given that their express purpose is to kill the players, rather than ransack the countryside at large, there's nothing to stop the players pulling back through the graveyard gate, sticking a tank in the doorway, and blasting the zombies with AoE attacks when the undead group up at the choke point. To some extent, that's the charm of the minion-heavy setup, but a quick look at the map suggests that this probably wasn't intended to be the dominant strategy.
 The Graveyard Exterior is a very poor follow-up to the Dead Walk, but it does make for a good opening to it. Take the monsters off the horrible default map and move them to Winterhaven, and have the players fighting the horde of zombies at the very gates of their home base. Once they've lifted the undead siege, the villagers direct them to the real source of the problem - the Graveyard.