Silent Witness season 25 episode 3 delivered a nasty surprise for Tom

Tom had acted as Sam's security detail in Stockholm back in 2018 when they were both working for the UN. A politician had been murdered, with Sam drafted in to carry out the post-mortem.

The culprits responsible for his death had also attempted to murder Sam's husband Jomo, but health secretary Alice Reynolds wound up dead instead. They also killed journalist Dan Clemence and Jomo's PA Rosa Hernandez.

Tom is also Nikki's ex-husband. The pair had been expecting a child together in their early 20s, but she suffered a stillbirth, which caused the breakdown of their relationship.

• Read more: Silent Witness season 25 episode 2 recap: the end of forensic science as we know it?

Tom confronted Sam about the vial of blood she had swiped from Nikki. The pathologist had collected several samples from the assassins' hotel room which indicated that they were involved in a DNA fabrication scheme.

"What is this?" he asked. "Where did you get it? Please tell me you're not involved in this?"

Once again, Sam stuck to the party line: "I'm trying to help you. I'm on your side. Trust me."

Tom then informed Sam that Sonia Karpov, the sister of dead Russian colonel Andrei Karpov who had taken his own life, had been found dead in prison.

Sonia blamed Tom for his death and set out to avenge her sibling by pinning all of the murders on him.

• Read more: David Caves on Silent Witness at 25: "This show could go on forever"

According to the evidence, she had also died by suicide, but Tom believed otherwise.

"These people won't think twice about making it look like we've done the same," he said to Sam.

Sam didn't offer any response to that news. Instead, she took back the vial and told Tom to come to her apartment on Saturday night. He followed her orders, seemingly believing that she could potentially help him, but there was a nasty surprise waiting for him.

When Tom arrived, he was swarmed by armed police while Sam watched on from a window.

Her motives are still unclear, as is the identity of the "they" who are pulling the strings. Given that Jomo was supposed to die, and not the health secretary, it's unlikely that Sam is the the Big Bad. If he had been killed, the Unitas Health contract, which had won the company a "data goldmine" integral to the success of their business, would have become null and void, which wouldn't have benefitted Sam. All of the evidence suggests that she works well with her husband and they share the same goal.

But there were rumblings of the pair having used unscrupulous means to build their company – it was alleged that the money they acquired to fund their endeavour was supplied by corrupt regimes which Jomo carried out election work for, with the couple rounding up Unitas investors while they were still working for the UN.

But what is certain is Sam knows a lot more than she's currently letting on. While she's unlikely to be an out and out villain (although our disbelief is suspended), she's not playing by the rules either.

Is that a survival tactic, with Sam taking steps, however legally dubious, to ensure that she makes it out of this unscathed, or is it solely for the benefit of her business and accumulating as much power as possible?

Tune in on Tuesday to find out what happens next.

Silent Witness season 25 episode 4 airs on Tuesday 31st May at 9pm on BBC One. Check out more of our Drama coverage or visit our TV Guide to see what's on tonight.

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