An employee, unless the term of his service has expired or unless he has a right to discontinue it at any time without notice, shall continue his service after notice of the death or incapacity of his employer, so far as is necessary to protect from serious injury the interests of the employer’s successor in interest, until a reasonable time after notice of the facts has been communicated to such successor. The successor shall compensate the employee for such service according to the terms of the contract of employment.