linux - Using wget to mirror a website and everything from the first level of external sites

I need to mirror a particular website (all the pages under that particular domain) any pages (but not whole sites) that the website links to.

I'm confused about the how to do this

wget -r --level=inf (or some other variant) will mirror the site.

wget -r -H --level=1 will get all the links (from all domains) to the first level.

Anyone have any ideas on how I could combine these, to get the entire of the main site and one level deep into external sites. I've been banging my head against the manual all afternoon.

Thanks