interquel

From inter- (“between”) +‎ quel, by analogy with prequel.

interquel (plural interquels)

1. (narratology) An installment in a series of works set chronologically between two of its predecessors.
2. (narratology) Any middle sequel with an earlier and a later installment.
   • For quotations using this term, see Citations:interquel.

• Of the second sense, this usage may not be proper.