The vital point here is that Richthofen time travels around and his plan is to kill all copy's of himself from making Samantha into the zombies overlord in the first place as he feels guilty for betraying his friend (maxis) and Samantha... Also Samantha after moon travels back in time in Richtofens body to tell maxis what Richtofens did then told the young versions of primus what we now see in 'The Giant' about Richtofen and his and Dr Maxis's plan of how to save the children... Samantha is one of the children, Eddie is also another version of Richtofen maybe his son, maybe his nephew or maybe an alternate time version of him our Richtofen got to look after Samntha... Either way the children is states in the shadow of evil is Samantha and Eddie and they must be kept safe this is an order presumably issued by Richtofen... But isn't Samantha supposed to hate Richtofen for what he did to her and got her Farther (Maxis) killed? Young Richtofen (The Giant) reimbershies the love she had for 'Uncle Richtofen' and now all Richtofens feel the duty to protect these children as without them the zombies and the discovery of element 115 will collapse in on the multiple dimensions caused by Richtofen... Edward Richtofens plan is to kill all versions of himself, and Maxis is helping him... But why do Eddie and Samantha have to be kept safe?
