IF you're seeing things, and it don't look good, who are you going to call?

Around Parkhead these days, it's John Guidetti.

It's a hot line which has been well used over the last few days, and last night was no exception.

With the hosts being held to a 0-0 stalemate by a plucky and confident Partick Thistle as they attempted to exorcise the demons of not winning the League Cup for five years years, the Swede produced a stunning free-kick to put his team into a lead which punctured any hopes the visitors had of a famous win.

Not content with this contribution which set Celtic on course for their first semi-final in this competition in two years, he sought to further add to his ever-growing reputation by repeating the feat seven minutes after the break before a spot kick two minutes later completed a master class which will have provided a bittersweet moment for his manager Ronny Deila.

The striker is only in Glasgow for this season until his year-long loan from Manchester City is at an end.

It's a match made in Paradise that Deila is keen on extending, with the Barclays Premier League champions rumoured to be looking at a £5million pre-contract deal if Celtic wanted to do a deal in January to make the move permanent.

With the likelihood that the Hoops board may want to wait until he is out of contract with City next summer in order to gain his services without the need of a transfer fee, they may well have to take their chances with competition from clubs south of the border for the talented 22-year-old's signature.

It's a list of potential suitors which will be growing by the day. Last night's hat-trick took his tally to eight goals in eight games, a truly remarkable figure given the former Feyenoord forward had barely kicked a football for two years.

While the Ghostbusters theme tune bizarrely rang round a sparsely-populated Celtic Park, Thistle were left haunted by Guidetti's contribution as he thrilled those who did brave the wintry Glasgow chill last night.

The match followed a similar template to that of Sunday's 2-0 SPFL Premiership win over Kilmarnock in that Celtic's attack seemed stilted in the face of Thistle's vibrancy.

Alan Archibald's men held their fair share of possession while restricting their hosts to many clear cut chances. The best of their play coming in a neat move down the right with the ball working its way to Nathan Eccleston and then James Craigen, only for the midfielder to shank his shot wide from the edge of the box.

It was time for Celtic to get out the phone.

On 30 minutes Guidetti drew a foul 25 yards out after being tripped by Abdul Osman. He dusted himself down to sumptuously bend the ball over the wall and into the net as Scott Fox's despairing dive couldn't keep it out.

Not long later he would make a different but equally crucial contribution as Stuart Bannigan crashed through the back of the Swede to receive a straight red card from Kevin Clancy.

It left the Hoops with a familiar task after a sending off and a Guidetti free-kick put them on their way to a win at the weekend.

Within three minutes of the restart it was game over as Emilio Izaguirre grabbed his first ever goal at Parkhead courtesy of a fine volley from 10 yards out.

It was only a brief interruption before Guidetti could continue his masterpiece in finishing, again curling a sublime free-kick over the wall from 25 yards into the top left corner with Fox this time rooted to the spot.

Just three minutes later his hat-trick was complete. A clumsy challenge again by Osman sent the striker clattering to the deck with the referee pointing to the spot. Guidetti's emphatic finish sending the Thistle keeper the wrong way as the ball rocketed into the roof of the net.

While the City loanee was done for the night, there was still time for others to get in on the act.

Leigh Griffiths was introduced for Anthony Stokes as he tries to win over Deila to gain a foothold back in the Celtic first team.

The former Hibernian man did himself no harm last night as he grabbed a brace to take his tally for the season to three.

His first came on 62 minutes as Izaguirre's deep cross from the left met his head perfectly at the back post, with the ball flying back across goal and into the net to make it five.

And with 68 minutes on the clock Griffiths rounded off a fine night for Celtic. Fox's attempted clearance wasn't released in time with it crashing off the in-rushing striker and into the back of the net.

It was a fortunate finish, but there was little that was lucky about the performance as the Premiership champions spurned countless more chances to inflict further misery on Thistle.

In truth, it didn't matter. The damage had already been done.