A Storm in a Teacup

Here you have a Fork and a tricky task. Solve it instead of tinkering with repairs.
One of Matvey Grishin's twin daughters fell ill. And during the treatment and tests, it turned out that he is not the genetic father of the girls. But this just can’t be! The shocked man rules out infidelity on his wife's part: Verusya and Natusiya are two exact copies of him: dark-skinned, dark-haired, brown-eyed... Grishin asks Viola to investigate this matter and clarify everything.
His head is spinning from these twins! Fork and Stepan began to shake out skeleton after skeleton from the closets of the strange family and stumbled upon… Matvey's double, a certain Boris Bogdanov. And just when the mystery was about to be uncovered - Boris is found dead. The case takes quite a serious turn.