“The Crossing” is episode ten of season one of Threshold.
A guard at the Threshold facility seems to make a mistake when feeding the infected prisoners, and three of them manage to escape. They are recaptured before they accomplish anything, but the secure facility is now ready, so the decision is made to transport the prisoners there.
The original plan was to transport the prisoners one at a time, but the new National Security Advisor, who was appointed in the previous episode, “Progeny”, overrules this, and states that they all have to be transported at once, and before everyone is ready. This hardly makes everyone else happy.
The missing captain of the Bighorn has, meanwhile, been recruiting former SpecOps soldiers, and launches a raid on the prisoner transport. The National Security Advisor, who seems to be a political micro-manager, blames everyone else for this, even though it if he’d gone along with the plan, it probably wouldn’t have happened.
The guard, Adams, who made the mistake actually turns out to be in the early stages of infection, and was seeing things. It’s not known how he came to be infected, though. He’s not the only one seeing things either – someone else is, and by comparing an interaction in this episode to the last one, it can be worked out who.