The Beast Within. Suzanne Mcminn

The thing he feared most lived inside him…PAX superagent Kieran Holt never wanted to leave his wife, Paige, but when a lab explosion turned him from scientist to experiment, he hid himself on a secret island to effect a reversal. Believing Kieran a traitor, Paige had spent the past two years searching for him–but now she wasn't the only one who'd found him.Pursued by a government agency, Kieran and Paige had one last chance to uncover the truth and save their marriage…But only if they could tame the beast within.