This story seems to forget one of the basic facts established about the aliens, in that they have to regenerate or they will die. David never even asks Anne if she needs to do this or when she is due. The aliens could have simply waited for her to come back to them in desperation or just let her die and their problem would be over. On the other hand, when they first got her, at the antique store, they could have just killed her right there on the spot and been done with her.
At the end of Act III Corwin calls his alien compatriots and tell them to look for David's helicopter which is going *from* Virginia. This doesn't make sense since they are currently in Massachusetts. Presumably he was supposed to say going *to* Virginia. But that raises another question: how did he know where they were going. While he knew they ultimately wanted to reach Washington, D.C., they could have been headed to Maryland or Delaware.
Hank Willis, a former Sheriff, leaves his gone out in the open in his car with the window rolled down. No former Sheriff would ever do something like this.