It's a remake of X-Men #3, when the X-Men first met the Blob.
The X-Men train in the Danger Room and Professor X brings in a new mutant; the Blob. The X-Men battle the Blob to run test. The Blob escapes and returns to the circus where he belongs. The X-Men go searching for Blob only to attack by Blob and the other circus freaks. The Professor X makes Blob and the rest of the circus forget they ever meet the X-Men.