...a system of plates buried vertically in the yard which are attached to plates on the inside basement wall by a threaded rod? If this is what you speak of, I'd advise against this method; under most circumstances it is not an effective repair.
To get an effective, permanent repair, plan on removing the finish along this wall, and possibly others, no matter the method used. There is never just one crack ; there will be at least two, and more likely 3 or more, but one may be particularly worse than the others.
Look for any evidence these finished walls were done recently, perhaps to disguise a problem. Ask the real estate agent about it; had the owners done work on the crack? Did they have water problems?
On the outside of the home, at the bottom of the siding, check how far it is to the concrete from the siding face at both ends, then at the center; this is usually a pretty good indicator if a wall is bowing in. If the exterior is brick, look for a bow in the brick inward at the floor line, or cracks in the bricks and mortar.
Have it looked at by a foundation repair specialist, and get thier opinion as to the status.
With corrected grading and drainage, it may be fine, or it may only need to be sealed, but it could also be an active situation which needs structural repair.