The Uncanny X-Men #193

Direct

Callisto rescues Professor X and returns him to the mansion decked out in Morlock gear (which the rest of the X-Men find incredibly funny). The Hellions capture Banshee and dare the X-Men to come and rescue him. The X-Men prevail but Thunderbird comes after Xavier in retaliation for his brother's death (way back in X-Men #95). Xavier talks him out of his quest for revenge and both Thunderbird and Firestar are asked to join the team (and both decline).