Editor's note: First Bite is a new concept in restaurant writing. This is not a go-three-times, try-everything-on-the-menu report; rather, this is a quick snapshot of a single experience. We invite you to come along with our writers as they—informed, intelligent eaters like yourselves—have a simple meal at an area restaurant, just like you do.

It's not surprising that the lobster roll at the Lobster Shack is good. The spiny crustacean is, after all, the centerpiece of the restaurant that opened this spring in Napa Valley. Owner Russell Deutsch, a former lobster exporter from Boston, uses quality Maine shellfish, plucked live from a tank on display in the restaurant. And he's got a loyal clientele, enough so that this is his third location (the others are in San Francisco and Redwood City).

What's curious is that it's not really, really good. I've had plenty of exquisite lobster rolls—from the classic with mayonnaise and chopped celery on a toasted, buttery hot dog bun to an Arizona real live "Iron Chef's" luxe rendition with avocado cream and garlic aioli on a Japanese-spiced Buddha roll. And when they're done well, lobster rolls can be things you insatiably crave.

But at the Shack, there's way too little meat tucked in the soft, New England–style top-loading hot dog bun. It tastes fine, with a light slick of mayo and a sprinkle of green onion, but the stinginess is unforgivable; served in a red plastic basket with very sweet, raisin-studded coleslaw and a pickle, it's an extraordinary $17.75. There are a lot of confusing things, actually, about the Shack. The awful location, for example. Tucked oddly inside the former Napa train depot turned grungy used car lot on a dingy corner of downtown, it's a whole lot of work to find. (Seriously, I was hoping to come out after dinner and find an offer on my heap, but no luck). And once there, it's just too mediocre to encourage making the effort again.

Carelessness is the main sin. Gazpacho, served in a chilled mug ($7), would have been quite tasty if it weren't so cold. I expected to find ice chips in the tomato broth spiked with lots of pepper and chunks of lobster, whole shrimp, bell pepper and chiles. The overpriced lobster macaroni and cheese ($16.75) was appealing for the first few bites, until the gritty sauce separated into oil rolling off the plump pasta shells. Crab cakes ($16.75) were excellent, thick with meat and fiercely spicy with remoulade; unfortunately, the red potatoes they nested on were bitter and old-tasting.

Perfect, cracker-breaded shrimp in the Captain's platter ($26.75) made up for the bland fried fish sharing the plate, but the soggy breaded soft-shell clams were an absolute disaster. Surely, they were off, smelling foul and tasting like ocean dredge. In hindsight, I should have sent them back, but I busied myself with the decent, skin-on steak fries instead.

I do like the casual, nautical interior, with its picnic tables in the back room, rolls of paper towels and self-serve water pitchers with plastic cups. I can envision fun times at the Shack, decked in a plastic bib while digging into the best meal here: an ample, whole steamed lobster ($27.75) with fries, coleslaw, corn on the cob and lots of hot drawn butter.

But until the kitchen gets a much better grip on quality control—or I'm in the market for a used car, I suppose—that's a theory I won't be testing.

Lobster Shack, 806 Fourth St., Napa. Lunch and dinner daily. 707.258.8200.

Send a letter to the editor about this story.