Associated (P) sued Towers (D) to recover damages for a failure to pay rent as required in a sublease agreement. P also sought a declaratory judgment regarding the extent of its obligation to supply D with electrical service. D moved to dismiss the complaint for a failure to join an indispensable party under Rule 12(b)(7). P failed to join the building's landlord, 417 Fifth Avenue Corp. During the pendency of the Rule, 12(b) and summary judgment motions D sued P and 417 Fifth Avenue Corp. The district court granted the motion and P appealed.