law: Specific Relief Act, 1963
  18. Non-enforcement except with variation
  Where a plaintiff seeks specific performance of a contract in
  
  writing, to which the defendant sets up a variation, the plaintiff cannot
  
  obtain the performance sought, except with the variation so set up, in the
  
  following cases, namely,-
  (a) where by fraud, mistake or fact or misrepresentation, the
  
  written contract of which performance is sought is in its terms or effect
  
  different from what the parties agreed to, or does not contain all the terms
  
  agreed to between the parties on the basis of which the defendant entered into
  
  the contract;
  (b) where the object of the parties was to produce a certain
  
  legal result which the contract as framed is not calculated to produce;
  (c) where the parties have subsequently to the execution of the
  
  contract, varied its terms.