I think I'm getting a bit further.

I modified this a bit and its redirecting but not carrying the parameters. Here's the updated config:

http {
server {
listen 80;
server_name abcd.com;
rewrite ^(.*) https://$host$1 permanent;
}
server {
listen 80;
server_name efgh.com;
rewrite ^(.*) https://abcd.com/referrals/$1 redirect;
}
server {
listen 443;
server_name abcd.com;
}
server {
listen 443;
server efgh.com
rewrite ^(.*) https://abcd.com/referrals/$1 permanent;
}
}
}
}