The seller can keep the deposit and sue for damages.
This is an older version of the standard AREA contract; see clause 9.1:
http://www.serlox.com/Forms/Offer.pdf
If the Seller or the Buyer fails or refuses to complete this Contract according to its terms, then the other party may pursue all available remedies. The Seller's remedies include keeping the Deposits and claiming additional damages. Both the Seller and the Buyer can claim reasonable costs including legal fees and disbursements on a solicitor/client full indemnity basis.