THE plot is really thickening in the Weir Group acquisition soap opera.

The Glasgow-based engineer's decision to part company with Bank of America Merrill Lynch, understood to have resulted from the broker's appointment by rival IMI, appears to have set up a real cliffhanger. And the focus is now very sharply on Weir's chief executive, Keith Cochrane.

While Weir's statement to the stock market this week on erstwhile joint broker Bank of America Merrill Lynch might have been short on detail, it appeared to be pretty long on attitude.

The company declared: "The Weir Group Plc has terminated its joint corporate broker engagement with Bank of America Merrill Lynch following the recent emergence of a new and undisclosed conflict of interest arising from its engagement as broker by another company."

Such a statement was always going to fuel speculation about just what might be occurring behind the scenes, and what on earth was going to happen next, and so it has proved.

Birmingham-based IMI has been touted as a bid target for Weir.

And, just for a bit of added spice, IMI is headed by Australian Mark Selway. Mr Selway was chief executive at Weir for eight years. He was also former Weir finance director Mr Cochrane's boss for a few years, so the pair presumably know each other well. It therefore goes without saying that, if FTSE-100 company Weir does have its eye on IMI, any game of cat and mouse between the pair will be fascinating.

Weir has made it plain it wants to be the cat, rather than the mouse, in any bid action. However, it has so far had about as much success as William Hanna and Joseph Barbera's tenacious Tom had in getting the better of Jerry.

And it appears it could just about as easily find itself cast as the mouse as the drama plays out, having been tipped as potential prey for bigger engineering companies such as GE, Siemens and ABB, with Caterpillar also cited in the past as a possible suitor.

Unfortunately for Weir, it has found itself chasing its tail in its acquisition efforts. Metso recently rejected a bid approach from Weir which valued the Finnish engineering company at about €4.5 billion (£3.6 billion).

On Thursday last week, Metso shares surged more than eight per cent on the back of strong second-quarter results. This coincided with a fall in Weir's shares, on mild disappointment over the Scottish company's first-half results, notably a lower profit margin.

Last month, there was talk that Weir might be weighing a bid for another Finnish company, Outotec, which produces pumps for the mining industry and has a stock market worth of €1.3 billion. Outotec said it had not received any approach from Weir.

The high-profile rejection from Metso, which looked like a good fit for Weir but was always a hard target with Finnish state investment company Solidium as a major and supportive shareholder, certainly highlighted to anyone who cared to look that Weir felt the need for a big acquisition.

Those likely to have been looking would obviously include potential bidders for Weir. And the nature and tone of the statement about Weir's relationship with Bank of America Merrill Lynch will likely have made the spotlight shine even more brightly on the Glasgow company.

The statement certainly grabbed the attention of Justin Haque, a director of Hobart Capital Markets in London.

In a note entitled "Weir - So touchy but is GE getting feely", he declared Weir's decision on Bank of America Merrill Lynch "illustrates that the company is really getting too neurotic to stay strongly independent for long".

This view might be a bit harsh but it signals that pressure is building on Mr Cochrane and his team.

Citing GE, Siemens and ABB, noting the level at which Weir shares were trading, and touching on the Glasgow company's expertise in providing equipment for exploitation of shale oil and gas reserves, Mr Haque said: "On 19 [times earnings], Weir is still the easy entry into European fracking and it's only a matter of time before one of the above-listed majors acts."

It is difficult to escape the notion that the clock is ticking for Mr Cochrane, in terms of landing a large acquisition on the right terms before one of the big players steps in for Weir.

That said, Weir shares have had a very strong run. If there is someone out there running the rule over the company, share-price strength would be the most important thing in making a suitor think twice about whether it might be over-paying. A strong share price should also aid Weir in finding an acquisition on the right terms.

Weir, a company with a proud heritage dating back to Victorian times, looks to be in a crucial phase.

The Metso rejection was undoubtedly a setback and the Bank of America Merrill Lynch situation has turned the heat up further.

But Mr Cochrane and Weir's board will also have to make sure the company is not perceived to be rushing to do a deal, or over-paying. This looks to be a high-stakes drama not just for Weir but for corporate Scotland. The importance of Weir's headquarters to Scotland cannot be underestimated.

Mr Cochrane, who has voiced concerns about the economic impact of a Yes vote in next month's referendum on Scottish constitutional change, looks to have his work cut out, but hopefully he will remain cool under pressure and deliver independence for Weir.