Tips for bringing in a new player

Hi all,

I've been running Strahd for about 7-8 months but recently had a player have to leave. I'm planning on bringing in a replacement, but struggling to workout how I can fit him into the story.

The group are currently in Valaki and are about to head to Wizard of Wines, Currently at Level 5. We haven't played for about a month due to players being away, so everyone has been on an extended break, so when I pick things up again everyone will probably be a little rusty.

Any ideas on a smooth introduction to a new player at this stage of the Campaign?