A non-competition agreement is a contract, and therefore provides whatever rights and imposes whatever obligations it, by its plain terms, provides or imposes--and *only* those rights and obligations. (You get any rights beyond those in the contract.) Therefore, to see whether this non-competition agreement provided any recourse against the employee for going to work for your client, you need to bring the agreement to an attorney who can review it and the situation with you. When you do so, also ask the attorney whether you may have any recourse for misappropriation of confidential information, if the employee used any confidential business obligation obtained only from his employment with you to get or perform the job; and in addition, ask also about--if the employee did wrongfully take or use any confidential business information to harm your business (e.g. cause his employer to pull the books from you)--whether that would support an action for tortious interference with economic advantage or with contract.