Buying Intego was a waste. AV programs do one thing well on Macs—makes them slow.
This article describes Search Marquis:
https://macresearch.org/what-is-search-marquis/
It can be manually removed
Removing "Search Marquis" / "Search Baron… - Apple Community
but, if that is too daunting, I recommend using the adware remover most senior contributors here recommend. Malwarebytes is a development of a trusted senior member and is one of the few third-party solutions most of us trust.
You catch search Marquis from using unscrupulous download hosting sites that promise you stuff free that you know would cost money elsewhere. To avoid more of the same, get MalwareBytes ONLY from the developer's site:
https://www.malwarebytes.com/mac
The free version is run manually; the pay-for version runs in the background to intercept incoming adware on the fly. If you wean yourself off those dicey hosting sites, you can probably get by with manual scanning.