Matilda

Matilda is a name mentioned by Van Ark and Paula at different times.

In the Abel 10k Race, Van Ark says (clip #8, Another Way)

I had to try to find Matilda, so I escaped! And came back here to see if she’d left me a message, which… she hadn’t.

Then, later (clip #9, A Few Moments):

Maxine - I think Matilda’s gone. But you and I can help with the research at the Jeffro Complex.

S2M32, Tightrope, clip #3, Van Ark says:

I really am impressed! All that leaping and ducking, like an episode of Total Wipeout. Matilda and I used to enjoy that program very much.

Van Ark's wife, Sigrid, mentions how Van Ark would often bring his girlfriends home, so it's likely Matilda was a women he was having an affair with.

S5M23, Hungry Like The Wolf, clip #5, Paula says:

Deeply in love with his wife was not the impression he gave around the labs. For one thing, there's Matilda.