Michael struggles to keep the abbey under control as the CDC team move closer toward tracking the source of the pathogen; at the same time, Alan fights the urge to rejoin his former colleagues and comes to terms with the reality about Peter's allegiances. In the future, Walker takes a risk attempting to escape her delusional father.

Peter reveals is brother's secret and gets them both in trouble; at the same time, Kyle has his hands full trying to quarantine the orchard and the infected hive.

The CDC team are forced to work together when another outbreak threatens to overwhelm the Abbey.