No, it's not a plural; it's the simple past subjunctive of "to be", which is "were" for all persons.  See my article from earlier today: https://ell.stackexchange.com/questions/151873/subject-inversion-in-the-correlative-comparative-construction, and my article from November 23rd regarding the subjunctive: https://ell.stackexchange.com/questions/148091/if-you-explained-what-you-trying-to-achieve-i-would/148110#148110.

Here are some examples of the subjunctive although some of them are a bit old-fashioned or archaic or highly formal:

> If **I were** the President of the United States, **I would** cut
> taxes. (both "were" and "would" are simple past subjunctives of "to
> be" and "will" respectively.)
> 
> If **I wanted** you to get involved, **I would** ask for your help.
> (both "wanted" and "would" are simple past subjunctives of "to want"
> and "will" respectively.)
> 
> If **I be elected** President, I shall cut taxes. ("be" is the simple
> present subjunctive of "to be".)
> 
> If **I were elected** President, **I should** cut taxes. ("were" and
> "should" are simple past subjunctives of "to be" and "shall".)
> 
> I shall do it if **he** so **want** me to. ("want" is the simple
> present subjunctive of "to want".)
> 
> It's important that **they be** on their best behavior. (simple
> present subjunctive)
> 
> I demand that **she answer** me! ("answer" is the simple present
> subjunctive of "to answer".)
> 
> O that **she were** mine! (simple past subjunctive)
> 
> If **I had gone** to the party, I **would** have had a great time.
> (past perfect subjunctive of "to go")
> 
> It's imperative that **he have finished** college by the time he is
> 23-years-old. (present perfect subjunctive of "to finish".)
> 
> He talks as though **he knew** everything there is about being in
> love. (simple past subjunctive of "to know".)
> 
> I wish **the subjunctive were used** more. (simple past subjunctive)
> 
> I pray that **the subjunctive be revived**. (simple present subjunctive)

The subjunctive is somewhat fancy and formal, but it is still considered good English today; in fact, in some instances, it is considered really good English.  It was more popular during the nineteenth and early twentieth centuries than it is today, although it's been experiencing somewhat of a revival since it is quite frequently used in American English, particularly the *mandative subjunctive*:

> I recommend that **she not do** that.

It is also very popular in literature, especially literature from the nineteenth century and earlier centuries:

> "Men's courses will foreshadow certain ends, to which, if persevered
> in, they must lead," said Scrooge. "But if **the courses be departed**
> from, the ends will change. Say it is thus with what you show me."
> *Ebenezer Scrooge, A Christmas Carol by Charles Dickens, 19 December 1843.*
> 
> "The basis of our governments [sic] being the opinion of the people,
> the very first object should be to keep that right; and **were it
> left** to me to decide whether we should have a government without
> newspapers, or newspapers without a government, **I should** not hesitate
> a moment to prefer the latter. But **I should** mean that every man should
> receive those papers and be capable of reading them." *Letter from
> Thomas Jefferson to Edward Carrington, 16 January 1787, Paris,
> France.*

I hope this might have helped you out.  If you should have any questions, please feel free to ask me.  Take care and good luck!

**P.S.** As many people on this forum know, I do not buy into the fabricated irrealis mood that some modern grammarians now adhere to.  I go by what it was in Old English and it clearly was the subjunctive in Old English; and just because the language has syncretized over the past 1,000 years doesn't mean it's not the subjunctive anymore: past subjunctive of "to be" in Old English: ic ƿǣre (I were); past indicative: ic ƿæs (I was). present indicative: ic eom (I am); present subjunctive: ic bēo (I be). This runic letter ƿ is wynn; it makes a w sound. Present indicative of "will": ic ƿille (I will); past subjunctive: ic ƿolde (I would); present indicative of "shall": ic sceal (I shall); past subjunctive: ic sceolde (I should).

And these are just a few verbs and only the conjugations in first-person singular; there are thousands of other verbs that also show this, but haven't been posited above.  Yes, English has syncretized over the past millennium, but it is still the subjunctive; the only problem is that the language has syncretized so much that one can only see the past subjunctive in the verb "to be" because it is the only verb in English whose past-tense inflections change depending on the person and whether the person be singular or plural.